Add chart trendlines.

.indent.pro

@@ -73,6 +73,7 @@
 -T lxw_chart_point
 -T lxw_chart_series
 -T lxw_chart_title
+-T lxw_chart_trendline_type
 -T lxw_chart_type
 -T lxw_col_options
 -T lxw_col_t

include/xlsxwriter/chart.h

@@ -832,6 +832,29 @@ typedef struct lxw_series_error_bars {
 
 } lxw_series_error_bars;
 
+/**
+ * @brief Series trendline/regression types.
+ */
+typedef enum lxw_chart_trendline_type {
+    /** Trendline type: Linear. */
+    LXW_CHART_TRENDLINE_TYPE_LINEAR,
+
+    /** Trendline type: Logarithm. */
+    LXW_CHART_TRENDLINE_TYPE_LOG,
+
+    /** Trendline type: Polynomial. */
+    LXW_CHART_TRENDLINE_TYPE_POLY,
+
+    /** Trendline type: Power. */
+    LXW_CHART_TRENDLINE_TYPE_POWER,
+
+    /** Trendline type: Exponential. */
+    LXW_CHART_TRENDLINE_TYPE_EXP,
+
+    /** Trendline type: Moving Average. */
+    LXW_CHART_TRENDLINE_TYPE_AVERAGE
+} lxw_chart_trendline_type;
+
 /**
  * @brief Struct to represent an Excel chart data series.
  *
@@ -871,6 +894,20 @@ typedef struct lxw_chart_series {
     lxw_series_error_bars *x_error_bars;
     lxw_series_error_bars *y_error_bars;
 
+    uint8_t has_trendline;
+    uint8_t has_trendline_forecast;
+    uint8_t has_trendline_equation;
+    uint8_t has_trendline_r_squared;
+    uint8_t has_trendline_intercept;
+    uint8_t trendline_type;
+    uint8_t trendline_value;
+    double trendline_forward;
+    double trendline_backward;
+    uint8_t trendline_value_type;
+    char *trendline_name;
+    lxw_chart_line *trendline_line;
+    double trendline_intercept;
+
     STAILQ_ENTRY (lxw_chart_series) list_pointers;
 
 } lxw_chart_series;
@@ -1758,6 +1795,24 @@ void chart_series_set_labels_num_format(lxw_chart_series *series,
 void chart_series_set_labels_font(lxw_chart_series *series,
                                   lxw_chart_font *font);
 
+void chart_series_set_trendline(lxw_chart_series *series, uint8_t type,
+                                uint8_t value);
+
+void chart_series_set_trendline_forecast(lxw_chart_series *series,
+                                         double forward, double backward);
+
+void chart_series_set_trendline_equation(lxw_chart_series *series);
+
+void chart_series_set_trendline_r_squared(lxw_chart_series *series);
+
+void chart_series_set_trendline_intercept(lxw_chart_series *series,
+                                          double intercept);
+
+void chart_series_set_trendline_name(lxw_chart_series *series, char *name);
+
+void chart_series_set_trendline_line(lxw_chart_series *series,
+                                     lxw_chart_line *line);
+
 /**
  * Set the X or Y error bars for a chart series.
  *

src/chart.c

@@ -120,6 +120,9 @@ _chart_series_free(lxw_chart_series *series)
         free(series->y_error_bars);
     }
 
+    free(series->trendline_line);
+    free(series->trendline_name);
+
     free(series);
 }
 
@@ -2108,10 +2111,9 @@ _chart_write_show_ser_name(lxw_chart *self)
 {
     struct xml_attribute_list attributes;
     struct xml_attribute *attribute;
-    char val[] = "1";
 
     LXW_INIT_ATTRIBUTES();
-    LXW_PUSH_ATTRIBUTES_STR("val", val);
+    LXW_PUSH_ATTRIBUTES_STR("val", "1");
 
     lxw_xml_empty_tag(self->file, "c:showSerName", &attributes);
 
@@ -2293,6 +2295,233 @@ _chart_write_d_lbls(lxw_chart *self, lxw_chart_series *series)
     lxw_xml_end_tag(self->file, "c:dLbls");
 }
 
+/*
+ * Write the <c:intercept> element.
+ */
+STATIC void
+_chart_write_intercept(lxw_chart *self, double value)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_DBL("val", value);
+
+    lxw_xml_empty_tag(self->file, "c:intercept", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:dispRSqr> element.
+ */
+STATIC void
+_chart_write_disp_rsqr(lxw_chart *self)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_STR("val", "1");
+
+    lxw_xml_empty_tag(self->file, "c:dispRSqr", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:trendlineLbl> element.
+ */
+STATIC void
+_chart_write_trendline_lbl(lxw_chart *self)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    lxw_xml_start_tag(self->file, "c:trendlineLbl", NULL);
+
+    lxw_xml_empty_tag(self->file, "c:layout", NULL);
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_STR("formatCode", "General");
+    LXW_PUSH_ATTRIBUTES_INT("sourceLinked", 0);
+
+    lxw_xml_empty_tag(self->file, "c:numFmt", &attributes);
+
+    lxw_xml_end_tag(self->file, "c:trendlineLbl");
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:dispEq> element.
+ */
+STATIC void
+_chart_write_disp_eq(lxw_chart *self)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_STR("val", "1");
+
+    lxw_xml_empty_tag(self->file, "c:dispEq", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:period> element.
+ */
+STATIC void
+_chart_write_period(lxw_chart *self, uint8_t value)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_INT("val", value);
+
+    lxw_xml_empty_tag(self->file, "c:period", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:forward> element.
+ */
+STATIC void
+_chart_write_forward(lxw_chart *self, double value)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_DBL("val", value);
+
+    lxw_xml_empty_tag(self->file, "c:forward", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:backward> element.
+ */
+STATIC void
+_chart_write_backward(lxw_chart *self, double value)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+    LXW_PUSH_ATTRIBUTES_DBL("val", value);
+
+    lxw_xml_empty_tag(self->file, "c:backward", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:name> element.
+ */
+STATIC void
+_chart_write_name(lxw_chart *self, char *name)
+{
+    lxw_xml_data_element(self->file, "c:name", name, NULL);
+}
+
+/*
+ * Write the <c:trendlineType> element.
+ */
+STATIC void
+_chart_write_trendline_type(lxw_chart *self, uint8_t type)
+{
+    struct xml_attribute_list attributes;
+    struct xml_attribute *attribute;
+
+    LXW_INIT_ATTRIBUTES();
+
+    if (type == LXW_CHART_TRENDLINE_TYPE_LOG)
+        LXW_PUSH_ATTRIBUTES_STR("val", "log");
+    else if (type == LXW_CHART_TRENDLINE_TYPE_POLY)
+        LXW_PUSH_ATTRIBUTES_STR("val", "poly");
+    else if (type == LXW_CHART_TRENDLINE_TYPE_POWER)
+        LXW_PUSH_ATTRIBUTES_STR("val", "power");
+    else if (type == LXW_CHART_TRENDLINE_TYPE_EXP)
+        LXW_PUSH_ATTRIBUTES_STR("val", "exp");
+    else if (type == LXW_CHART_TRENDLINE_TYPE_AVERAGE)
+        LXW_PUSH_ATTRIBUTES_STR("val", "movingAvg");
+    else
+        LXW_PUSH_ATTRIBUTES_STR("val", "linear");
+
+    lxw_xml_empty_tag(self->file, "c:trendlineType", &attributes);
+
+    LXW_FREE_ATTRIBUTES();
+}
+
+/*
+ * Write the <c:trendline> element.
+ */
+STATIC void
+_chart_write_trendline(lxw_chart *self, lxw_chart_series *series)
+{
+    if (!series->has_trendline)
+        return;
+
+    lxw_xml_start_tag(self->file, "c:trendline", NULL);
+
+    /* Write the c:name element. */
+    if (series->trendline_name)
+        _chart_write_name(self, series->trendline_name);
+
+    /* Write the c:spPr element. */
+    _chart_write_sp_pr(self, series->trendline_line, NULL, NULL);
+
+    /* Write the c:trendlineType element. */
+    _chart_write_trendline_type(self, series->trendline_type);
+
+    /* Write the c:order element. */
+    if (series->trendline_type == LXW_CHART_TRENDLINE_TYPE_POLY
+        && series->trendline_value >= 2) {
+
+        _chart_write_order(self, series->trendline_value);
+    }
+
+    /* Write the c:period element. */
+    if (series->trendline_type == LXW_CHART_TRENDLINE_TYPE_AVERAGE
+        && series->trendline_value >= 2) {
+
+        _chart_write_period(self, series->trendline_value);
+    }
+
+    if (series->has_trendline_forecast) {
+        /* Write the c:forward element. */
+        _chart_write_forward(self, series->trendline_forward);
+
+        /* Write the c:backward element. */
+        _chart_write_backward(self, series->trendline_backward);
+    }
+
+    /* Write the c:intercept element. */
+    if (series->has_trendline_intercept)
+        _chart_write_intercept(self, series->trendline_intercept);
+
+    /* Write the c:dispRSqr element. */
+    if (series->has_trendline_r_squared)
+        _chart_write_disp_rsqr(self);
+
+    if (series->has_trendline_equation) {
+        /* Write the c:dispEq element. */
+        _chart_write_disp_eq(self);
+
+        /* Write the c:trendlineLbl element. */
+        _chart_write_trendline_lbl(self);
+
+    }
+
+    lxw_xml_end_tag(self->file, "c:trendline");
+}
+
 /*
  * Write the <c:val> element.
  */
@@ -2501,10 +2730,9 @@ _chart_write_marker_value(lxw_chart *self)
 {
     struct xml_attribute_list attributes;
     struct xml_attribute *attribute;
-    char val[] = "1";
 
     LXW_INIT_ATTRIBUTES();
-    LXW_PUSH_ATTRIBUTES_STR("val", val);
+    LXW_PUSH_ATTRIBUTES_STR("val", "1");
 
     lxw_xml_empty_tag(self->file, "c:marker", &attributes);
 
@@ -2655,6 +2883,9 @@ _chart_write_ser(lxw_chart *self, lxw_chart_series *series)
     /* Write the c:dLbls element. */
     _chart_write_d_lbls(self, series);
 
+    /* Write the c:trendline element. */
+    _chart_write_trendline(self, series);
+
     /* Write the c:errBars element. */
     _chart_write_error_bars(self, series);
 
@@ -2704,6 +2935,9 @@ _chart_write_xval_ser(lxw_chart *self, lxw_chart_series *series)
     /* Write the c:dLbls element. */
     _chart_write_d_lbls(self, series);
 
+    /* Write the c:trendline element. */
+    _chart_write_trendline(self, series);
+
     /* Write the c:errBars element. */
     _chart_write_error_bars(self, series);
 
@@ -2937,10 +3171,9 @@ _chart_write_auto(lxw_chart *self)
 {
     struct xml_attribute_list attributes;
     struct xml_attribute *attribute;
-    char val[] = "1";
 
     LXW_INIT_ATTRIBUTES();
-    LXW_PUSH_ATTRIBUTES_STR("val", val);
+    LXW_PUSH_ATTRIBUTES_STR("val", "1");
 
     lxw_xml_empty_tag(self->file, "c:auto", &attributes);
 
@@ -5177,6 +5410,153 @@ chart_series_set_labels_font(lxw_chart_series *series, lxw_chart_font *font)
     series->label_font = _chart_convert_font_args(font);
 }
 
+/*
+ * Set the trendline for a chart series.
+ */
+void
+chart_series_set_trendline(lxw_chart_series *series, uint8_t type,
+                           uint8_t value)
+{
+    if (type == LXW_CHART_TRENDLINE_TYPE_POLY
+        || type == LXW_CHART_TRENDLINE_TYPE_POLY) {
+
+        if (value < 2) {
+            LXW_WARN("chart_series_set_trendline(): order/period value must "
+                     "be >= 2 for Polynomial and Moving Average types");
+            return;
+        }
+
+        series->trendline_value_type = type;
+    }
+
+    series->has_trendline = LXW_TRUE;
+    series->trendline_type = type;
+    series->trendline_value = value;
+}
+
+/*
+ * Set the trendline forecast for a chart series.
+ */
+void
+chart_series_set_trendline_forecast(lxw_chart_series *series, double forward,
+                                    double backward)
+{
+    if (!series->has_trendline) {
+        LXW_WARN("chart_series_set_trendline_forecast(): trendline type "
+                 "must be set first using chart_series_set_trendline()");
+        return;
+    }
+
+    if (series->trendline_type == LXW_CHART_TRENDLINE_TYPE_AVERAGE) {
+        LXW_WARN("chart_series_set_trendline(): forecast isn't available "
+                 "in Excel for a Moving Average trendline");
+        return;
+    }
+
+    series->has_trendline_forecast = LXW_TRUE;
+    series->trendline_forward = forward;
+    series->trendline_backward = backward;
+}
+
+/*
+ * Display the equation for a series trendline.
+ */
+void
+chart_series_set_trendline_equation(lxw_chart_series *series)
+{
+    if (!series->has_trendline) {
+        LXW_WARN("chart_series_set_trendline_equation(): trendline type "
+                 "must be set first using chart_series_set_trendline()");
+        return;
+    }
+
+    if (series->trendline_type == LXW_CHART_TRENDLINE_TYPE_AVERAGE) {
+        LXW_WARN("chart_series_set_trendline_equation(): equation isn't "
+                 "available in Excel for a Moving Average trendline");
+        return;
+    }
+
+    series->has_trendline_equation = LXW_TRUE;
+}
+
+/*
+ * Display the R squared value for a series trendline.
+ */
+void
+chart_series_set_trendline_r_squared(lxw_chart_series *series)
+{
+    if (!series->has_trendline) {
+        LXW_WARN("chart_series_set_trendline_r_squared(): trendline type "
+                 "must be set first using chart_series_set_trendline()");
+        return;
+    }
+
+    if (series->trendline_type == LXW_CHART_TRENDLINE_TYPE_AVERAGE) {
+        LXW_WARN("chart_series_set_trendline_r_squared(): R squared isn't "
+                 "available in Excel for a Moving Average trendline");
+        return;
+    }
+
+    series->has_trendline_r_squared = LXW_TRUE;
+}
+
+/*
+ * Set the trendline intercept for a chart series.
+ */
+void
+chart_series_set_trendline_intercept(lxw_chart_series *series,
+                                     double intercept)
+{
+    if (!series->has_trendline) {
+        LXW_WARN("chart_series_set_trendline_intercept(): trendline type "
+                 "must be set first using chart_series_set_trendline()");
+        return;
+    }
+
+    if (series->trendline_type != LXW_CHART_TRENDLINE_TYPE_EXP
+        && series->trendline_type != LXW_CHART_TRENDLINE_TYPE_LINEAR
+        && series->trendline_type != LXW_CHART_TRENDLINE_TYPE_POLY) {
+        LXW_WARN("chart_series_set_trendline_intercept(): intercept is only "
+                 "available in Excel for Exponential, Linear and Polynomial "
+                 "trendline types");
+        return;
+    }
+
+    series->has_trendline_intercept = LXW_TRUE;
+    series->trendline_intercept = intercept;
+}
+
+/*
+ * Set a line type for a series trendline.
+ */
+void
+chart_series_set_trendline_name(lxw_chart_series *series, char *name)
+{
+    if (!name)
+        return;
+
+    /* Free any previously allocated resource. */
+    free(series->trendline_name);
+
+    series->trendline_name = lxw_strdup(name);
+}
+
+/*
+ * Set a line type for a series trendline.
+ */
+void
+chart_series_set_trendline_line(lxw_chart_series *series,
+                                lxw_chart_line *line)
+{
+    if (!line)
+        return;
+
+    /* Free any previously allocated resource. */
+    free(series->trendline_line);
+
+    series->trendline_line = _chart_convert_line_args(line);
+}
+
 /*
  * Set the error bars and type for a chart series.
  */
@@ -5686,7 +6066,7 @@ chart_legend_delete_series(lxw_chart *self, int16_t delete_series[])
     if (delete_series == NULL)
         return LXW_ERROR_NULL_PARAMETER_IGNORED;
 
-    while (delete_series[count] > 0)
+    while (delete_series[count] >= 0)
         count++;
 
     if (count == 0)

test/functional/src/test_chart_format08.c

@@ -0,0 +1,50 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format08.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 46164608;
+    chart->axis_id_2 = 46176128;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format10.c

@@ -0,0 +1,55 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format10.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 54795648;
+    chart->axis_id_2 = 56296960;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .width     = 1,
+                           .dash_type = LXW_CHART_LINE_DASH_LONG_DASH};
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+    chart_series_set_trendline_line(series, &line);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format11.c

@@ -0,0 +1,57 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format11.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 50664576;
+    chart->axis_id_2 = 50666496;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .width     = 1,
+                           .dash_type = LXW_CHART_LINE_DASH_LONG_DASH};
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_POLY, 2);
+    chart_series_set_trendline_line(series, &line);
+    chart_series_set_trendline_name(series, "My trend name");
+    chart_series_set_trendline_forecast(series, 0.5, 0.5);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format12.c

@@ -0,0 +1,56 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format12.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 54794880;
+    chart->axis_id_2 = 56296576;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .width     = 1,
+                           .dash_type = LXW_CHART_LINE_DASH_LONG_DASH};
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_AVERAGE, 2);
+    chart_series_set_trendline_line(series, &line);
+    chart_series_set_trendline_forecast(series, 0.5, 0.5);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format13.c

@@ -0,0 +1,50 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format13.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 51785088;
+    chart->axis_id_2 = 51804032;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_labels(series);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format14.c

@@ -0,0 +1,51 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format14.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 51819264;
+    chart->axis_id_2 = 52499584;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_labels(series);
+    chart_series_set_labels_options(series, LXW_TRUE, LXW_TRUE, LXW_TRUE);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format15.c

@@ -0,0 +1,53 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format15.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 42401792;
+    chart->axis_id_2 = 42403712;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+
+    int16_t names[] = {2, 0, -1};
+    chart_legend_delete_series(chart, names);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format16.c

@@ -0,0 +1,52 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format16.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 43943040;
+    chart->axis_id_2 = 44287488;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_labels(series);
+    chart_series_set_labels_options(series, LXW_TRUE, LXW_TRUE, LXW_TRUE);
+    chart_series_set_labels_position(series, LXW_CHART_LABEL_POSITION_CENTER);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format19.c

@@ -0,0 +1,45 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format19.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_COLUMN_STACKED);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 56127488;
+    chart->axis_id_2 = 57455360;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    chart_series_set_labels(series);
+    chart_series_set_labels_position(series, LXW_CHART_LABEL_POSITION_INSIDE_BASE);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format20.c

@@ -0,0 +1,59 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format20.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart1 = workbook_add_chart(workbook, LXW_CHART_LINE);
+    lxw_chart     *chart2 = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart1->axis_id_1 = 80553856;
+    chart1->axis_id_2 = 80555392;
+
+    chart2->axis_id_1 = 84583936;
+    chart2->axis_id_2 = 84585856;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series1 = chart_add_series(chart1, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart1, NULL, "=Sheet1!$C$1:$C$5");
+
+    lxw_chart_series *series2 = chart_add_series(chart2, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart2, NULL, "=Sheet1!$C$1:$C$5");
+
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .dash_type = LXW_CHART_LINE_DASH_DASH};
+
+    chart_series_set_trendline(series1, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+    chart_series_set_trendline_line(series1, &line);
+    chart_series_set_trendline(series2, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+    chart_series_set_trendline_line(series2, &line);
+
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart1);
+    worksheet_insert_chart(worksheet, CELL("E25"), chart2);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format26.c

@@ -0,0 +1,54 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format26.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 108652416;
+    chart->axis_id_2 = 108655744;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+    chart_series_set_trendline_equation(series);
+
+    int16_t names[] = {2, 0, -1};
+    chart_legend_delete_series(chart, names);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format27.c

@@ -0,0 +1,58 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format27.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 108645376;
+    chart->axis_id_2 = 108655360;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .width     = 1,
+                           .dash_type = LXW_CHART_LINE_DASH_LONG_DASH};
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_POLY, 2);
+    chart_series_set_trendline_line(series, &line);
+    chart_series_set_trendline_name(series, "My trend name");
+    chart_series_set_trendline_forecast(series, 0.5, 0.5);
+    chart_series_set_trendline_equation(series);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format28.c

@@ -0,0 +1,55 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format28.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 108645376;
+    chart->axis_id_2 = 108655360;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+    chart_series_set_trendline_equation(series);
+    chart_series_set_trendline_r_squared(series);
+
+    int16_t names[] = {0, 2, -1};
+    chart_legend_delete_series(chart, names);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format29.c

@@ -0,0 +1,59 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format29.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 108652416;
+    chart->axis_id_2 = 108655744;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .width     = 1,
+                           .dash_type = LXW_CHART_LINE_DASH_LONG_DASH};
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_POLY, 2);
+    chart_series_set_trendline_line(series, &line);
+    chart_series_set_trendline_name(series, "My trend name");
+    chart_series_set_trendline_forecast(series, 0.5, 0.5);
+    chart_series_set_trendline_equation(series);
+    chart_series_set_trendline_r_squared(series);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format30.c

@@ -0,0 +1,56 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format30.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 108652416;
+    chart->axis_id_2 = 108655744;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_LINEAR, 0);
+    chart_series_set_trendline_equation(series);
+    chart_series_set_trendline_r_squared(series);
+    chart_series_set_trendline_intercept(series, 0.8);
+
+    int16_t names[] = {0, 2, -1};
+    chart_legend_delete_series(chart, names);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_format31.c

@@ -0,0 +1,60 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2017, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_format31.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_LINE);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 115443200;
+    chart->axis_id_2 = 115459200;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$B$1:$B$5"
+    );
+
+    chart_add_series(chart,
+         "=Sheet1!$A$1:$A$5",
+         "=Sheet1!$C$1:$C$5"
+    );
+
+    lxw_chart_line line = {.color     = LXW_COLOR_RED,
+                           .width     = 1,
+                           .dash_type = LXW_CHART_LINE_DASH_LONG_DASH};
+
+    chart_series_set_trendline(series, LXW_CHART_TRENDLINE_TYPE_POLY, 2);
+    chart_series_set_trendline_line(series, &line);
+    chart_series_set_trendline_name(series, "My trend name");
+    chart_series_set_trendline_forecast(series, 0.5, 0.5);
+    chart_series_set_trendline_equation(series);
+    chart_series_set_trendline_r_squared(series);
+    chart_series_set_trendline_intercept(series, 1.5);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/test_chart_format.py

@@ -34,12 +34,35 @@ class TestCompareXLSXFiles(base_test_class.XLSXBaseTest):
     def test_chart_format07(self):
         self.run_exe_test('test_chart_format07')
 
-
+    def test_chart_format08(self):
+        self.run_exe_test('test_chart_format08')
 
     def test_chart_format09(self):
         self.run_exe_test('test_chart_format09')
 
+    def test_chart_format10(self):
+        self.run_exe_test('test_chart_format10')
 
+    def test_chart_format11(self):
+        self.run_exe_test('test_chart_format11')
+
+    def test_chart_format12(self):
+        self.run_exe_test('test_chart_format12')
+
+    def test_chart_format13(self):
+        self.run_exe_test('test_chart_format13')
+
+    def test_chart_format14(self):
+        self.run_exe_test('test_chart_format14')
+
+    def test_chart_format14(self):
+        self.run_exe_test('test_chart_format14')
+
+    def test_chart_format15(self):
+        self.run_exe_test('test_chart_format15')
+
+    def test_chart_format16(self):
+        self.run_exe_test('test_chart_format16')
 
     def test_chart_format17(self):
         self.run_exe_test('test_chart_format17')
@@ -47,6 +70,12 @@ class TestCompareXLSXFiles(base_test_class.XLSXBaseTest):
     def test_chart_format18(self):
         self.run_exe_test('test_chart_format18')
 
+    def test_chart_format19(self):
+        self.run_exe_test('test_chart_format19')
+
+    def test_chart_format20(self):
+        self.run_exe_test('test_chart_format20')
+
     def test_chart_format21(self):
         self.run_exe_test('test_chart_format21')
 
@@ -61,3 +90,21 @@ class TestCompareXLSXFiles(base_test_class.XLSXBaseTest):
 
     def test_chart_format25(self):
         self.run_exe_test('test_chart_format25')
+
+    def test_chart_format26(self):
+        self.run_exe_test('test_chart_format26')
+
+    def test_chart_format27(self):
+        self.run_exe_test('test_chart_format27')
+
+    def test_chart_format28(self):
+        self.run_exe_test('test_chart_format28')
+
+    def test_chart_format29(self):
+        self.run_exe_test('test_chart_format29')
+
+    def test_chart_format30(self):
+        self.run_exe_test('test_chart_format30')
+
+    def test_chart_format31(self):
+        self.run_exe_test('test_chart_format31')