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  packPlotArea and multi charts
Posted by sroeber on Feb-28-2025 19:40
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Hi,

I have a problem with multiple charts and the packPlotArea() function. If I call packPlotArea(), it may cause the left side of the plot area to differ between the charts. How can I ensure that all charts start at the same x-position? Without using packPlotArea(), I would need to set the x offset in setPlotArea() manually depending on the values/width of the y-axis.

Best regards
Steffen

  Re: packPlotArea and multi charts
Posted by Peter Kwan on Mar-01-2025 00:00
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Hi Soreber,

packPlotArea always pack the plot area, including the axis labels and axis title, to within a given bounding box. As the label length can be different between charts, if you use the same bounding box, the left x-axis of the charts may not align.

After some thoughts, I think of the following method, which I have tried myself and it works in my case.

As I am not sure which programming language you are using, I randomly choose to use C# in the code example below:

Suppose you have 3 XYCharts, which are to be added to the MultiChart:

XYChart c[] = { c0, c1, c2 };

//Pack the plot area, and determine the chart with the smallest plot area width. This
//is the chart with the longest x-axis labels
int minPlotAreaWidth = 9999999999;
for (int i = 0; i < c.Length; ++i) {
    c[i].packPlotArea(leftX, topY, rightX, bottomY);
    minPlotAreaWidth = Math.Min(minWidth, c[i].getPlotArea().getWidth());
}

//For charts that have longer plot area width, they should be packed again with a
//smaller bounding box to make it the same width as the other charts.
for (int i = 0; i < c.Length; ++i) {
    int extraWidth = c[i].getPlotArea().getWidth() - minPlotAreaWidth;
    if (extraWidth > 0)
        c[i].packPlotArea(leftX+extraWidth, topY, rightX, bottomY);
}


If you need to translate the code to another programming language, please let me know.

Best Regards
Peter Kwan

  Re: packPlotArea and multi charts
Posted by sroeber on Mar-03-2025 15:46
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Hi Peter,

thanks that works for me as well.