Customize Data Points in Treemap and Sunburst Charts in Python

Overview

Treemap and Sunburst charts display the same kind of hierarchical data, but they use different layouts. A Treemap draws the hierarchy as nested rectangles whose areas represent leaf values. A Sunburst draws it as concentric rings: top-level groups are near the center, and leaf categories are on the outer ring.

In Aspose.Slides for Python via .NET, each numeric value is a ChartDataPoint. Its ChartDataPoint.data_point_levels collection provides access to the leaf and its parent groups. This article explains that mapping and shows how to create and format both chart types from the same sample data.

A Treemap chart with Consumer and Business branches

A Sunburst chart with the same Consumer and Business hierarchy

Understand Categories, Data Points, and Levels

The sample used below has three category levels and one numeric series:

Branch	Stem	Leaf	Revenue
Consumer	Computers	Laptops	12
Consumer	Computers	Desktops	8
Consumer	Mobile	Phones	15
Consumer	Mobile	Tablets	6
Business	Services	Consulting	10
Business	Services	Support	7
Business	Software	Licenses	11
Business	Software	Subscriptions	14

Each row creates one leaf category and one data point. The category grouping levels describe the path from that leaf to its parents. For the first row, the path is Consumer > Computers > Laptops.

The indexes in ChartDataPoint.data_point_levels run from the leaf upward:

`data_point_levels` index	Logical level	Treemap representation	Sunburst representation
`0`	Leaf	Value rectangle	Outer-ring segment
`1`	Stem	Parent rectangle or header	Middle-ring segment
`2`	Branch	Top-level rectangle or header	Inner-ring segment

This order is the same for both chart types even though their visual layouts differ. A parent segment is shared by several leaves. To format it, use the corresponding level of the first data point in that group. For example, the Consumer branch starts with the Laptops point, while the Software stem starts with the Licenses point. Keeping references to those points is clearer and safer than using unexplained expressions such as data_points[0] or data_points[6].

Create and Customize Both Chart Types

The following complete example creates a Treemap on the first slide and a Sunburst on the second slide. It builds the hierarchy, displays the value for Tablets, applies fixed colors to selected levels, formats a branch label, and saves the presentation.

import aspose.pydrawing as drawing
import aspose.slides as slides
import aspose.slides.charts as charts


def set_solid_fill(fill_format, color):
    fill_format.fill_type = slides.FillType.SOLID
    fill_format.solid_fill_color.color = color


def add_hierarchy_chart(slide, chart_type):
    worksheet_index = 0
    leaf_level_index = 0
    stem_level_index = 1
    branch_level_index = 2

    chart = slide.shapes.add_chart(chart_type, 40, 40, 640, 440)
    chart.has_title = False
    chart.has_legend = False
    chart.chart_data.categories.clear()
    chart.chart_data.series.clear()

    workbook = chart.chart_data.chart_data_workbook
    workbook.clear(worksheet_index)

    def add_category(row_index, leaf_name):
        category_cell = workbook.get_cell(worksheet_index, row_index, 2, leaf_name)
        return chart.chart_data.categories.add(category_cell)

    # Add the leaf categories. A grouping item is set only when a new group begins;
    # the following categories remain in that group until another item is set.
    laptops_category = add_category(1, "Laptops")
    laptops_category.grouping_levels.set_grouping_item(stem_level_index, "Computers")
    laptops_category.grouping_levels.set_grouping_item(branch_level_index, "Consumer")

    add_category(2, "Desktops")

    phones_category = add_category(3, "Phones")
    phones_category.grouping_levels.set_grouping_item(stem_level_index, "Mobile")

    add_category(4, "Tablets")

    consulting_category = add_category(5, "Consulting")
    consulting_category.grouping_levels.set_grouping_item(stem_level_index, "Services")
    consulting_category.grouping_levels.set_grouping_item(branch_level_index, "Business")

    add_category(6, "Support")

    licenses_category = add_category(7, "Licenses")
    licenses_category.grouping_levels.set_grouping_item(stem_level_index, "Software")

    add_category(8, "Subscriptions")

    series_name_cell = workbook.get_cell(worksheet_index, 0, 3, "Revenue")
    series = chart.chart_data.series.add(series_name_cell, chart_type)
    series.labels.default_data_label_format.show_category_name = True

    def add_data_point(row_index, value):
        value_cell = workbook.get_cell(worksheet_index, row_index, 3, value)

        if chart_type == charts.ChartType.TREEMAP:
            return series.data_points.add_data_point_for_treemap_series(value_cell)

        return series.data_points.add_data_point_for_sunburst_series(value_cell)

    laptops_data_point = add_data_point(1, 12)
    add_data_point(2, 8)
    add_data_point(3, 15)
    tablets_data_point = add_data_point(4, 6)
    add_data_point(5, 10)
    add_data_point(6, 7)
    licenses_data_point = add_data_point(7, 11)
    add_data_point(8, 14)

    # Show the category and value on the Tablets leaf.
    tablets_label_format = tablets_data_point.data_point_levels[leaf_level_index].label.data_label_format
    tablets_label_format.show_category_name = True
    tablets_label_format.show_value = True
    tablets_label_format.separator = "\n"
    tablets_label_format.number_format = "$0"

    # Format the Consumer branch through the first leaf in that branch.
    consumer_branch_level = laptops_data_point.data_point_levels[branch_level_index]
    consumer_branch_fill = consumer_branch_level.format.fill
    consumer_branch_color = drawing.Color.from_argb(31, 78, 121)
    set_solid_fill(consumer_branch_fill, consumer_branch_color)

    consumer_label_format = consumer_branch_level.label.data_label_format
    consumer_label_format.show_category_name = True
    consumer_label_format.show_series_name = False
    consumer_label_text_fill = consumer_label_format.text_format.portion_format.fill_format
    set_solid_fill(consumer_label_text_fill, drawing.Color.white)

    # Format the Software stem through the first leaf in that stem.
    software_stem_level = licenses_data_point.data_point_levels[stem_level_index]
    software_stem_fill = software_stem_level.format.fill
    software_stem_color = drawing.Color.from_argb(112, 173, 71)
    set_solid_fill(software_stem_fill, software_stem_color)

    # parent_label_layout affects Treemap parent labels; Sunburst uses ring segments.
    if chart_type == charts.ChartType.TREEMAP:
        series.parent_label_layout = charts.ParentLabelLayoutType.OVERLAPPING


with slides.Presentation() as presentation:
    treemap_slide = presentation.slides[0]
    add_hierarchy_chart(treemap_slide, charts.ChartType.TREEMAP)

    layout_slide = presentation.layout_slides[0]
    sunburst_slide = presentation.slides.add_empty_slide(layout_slide)
    add_hierarchy_chart(sunburst_slide, charts.ChartType.SUNBURST)

    presentation.save("hierarchical-charts.pptx", slides.export.SaveFormat.PPTX)

The category cells and value cells use the same worksheet row, so their collection positions remain aligned. When you work with an existing chart rather than creating one, inspect the category rows first and store named references to the data points and levels you intend to format.

Behavior and Practical Considerations

Treemap and Sunburst Differences

A Treemap uses area to communicate value and nested rectangles to communicate hierarchy. The ChartSeries.parent_label_layout property controls how parent labels appear in this chart type.
A Sunburst uses angle to communicate value and ring depth to communicate hierarchy. ChartSeries.parent_label_layout does not control its ring labels.
Both chart types use the same category grouping levels and the same leaf-to-parent order in data_point_levels, so the data-building and level-formatting code can be shared.
Parent values are calculated from their descendant leaves. Do not add separate numeric points for branches or stems.

Sorting and Segment Order

The chart layout engine determines the final placement of rectangles and ring segments. Arrange related category rows together before adding them, but do not rely on a specific rectangle position or start angle. If sequence carries meaning, include it in the labels or use a chart type with an explicit category axis.

Theme and Fixed Colors

Unformatted chart levels inherit colors from the presentation theme. The example uses explicit RGB fills for predictable output. If the chart should follow theme changes, use scheme colors instead of fixed RGB values and avoid overriding every level. Also check label contrast after changing a branch or stem fill.

Labels and Available Space

PowerPoint may hide or truncate labels when a segment is too small. Increasing the chart size, shortening category names, or showing fewer label fields usually produces a clearer result. A label can combine the category name, series name, and value through DataLabelFormat, but enabling every field often makes hierarchical charts difficult to read.

Export and Rendering

Saving to PPTX keeps the chart editable. When Aspose.Slides renders the presentation to PDF or an image, the supported fills and label settings are rendered with the chart. Font substitution and small differences in available layout space can change line wrapping or label visibility, so install the required fonts and verify important export targets.

FAQ

Why does changing a parent level affect several leaves?

A branch or stem is a shared visual segment. Its ChartDataPointLevel can be reached through a descendant leaf, but the formatting belongs to the shared parent segment rather than only to that leaf.

Why is a data label missing?

First enable the required fields on the label’s DataLabelFormat object. Then check whether the segment has enough space. Treemap parent-label layout, chart dimensions, label length, font size, and the number of enabled fields all affect whether a label can be displayed.

Can I set the exact order or coordinates of segments?

You can control the source-row order and keep each group contiguous, but you cannot assign exact Treemap rectangles or Sunburst angles. The chart layout engine calculates them from the hierarchy, values, and available space.

Why do colors change after the presentation theme changes?

Theme-based fills are designed to follow the presentation palette. Apply explicit RGB colors to the levels that must remain fixed, or keep scheme colors when adapting to a new theme is preferred.

Will custom formatting be preserved in PDF and image exports?

Yes, supported chart fills and label settings are included during rendering. For consistent results across systems, make the required fonts available and test the final export size because label fitting is layout-dependent.