Are there any plans to improve the chart drawing funtion

[EOOOL]

For example, I didn't find the ability to draw smooth scatter plots and x/y axis titles

[tonyqus]

how to define "smooth"? any requirement?

[EOOOL]

[mostmand]

Similarly, I need Stacked Column chart and 100% Stacked Column charts that there seems to be no option for. NPOI creates Clustered Column charts by default with no option to change that.
When I was searching for it I faced this discussion that is about this thing in apache POI and it supports it by calling setBarGrouping(BarGrouping.STACKED) on the BarChartData class.

[mostmand]

I looked at the source code. In the XSSFBarChartData.Series class there is a method called AddToChart which is like this:

internal void AddToChart(CT_BarChart ctBarChart)
{
    CT_BarSer ctBarSer = ctBarChart.AddNewSer();
    CT_BarGrouping ctGrouping = ctBarChart.AddNewGrouping();
    ctGrouping.val = ST_BarGrouping.clustered;
    ctBarSer.AddNewIdx().val = (uint)id;
    ctBarSer.AddNewOrder().val = (uint)order;
    CT_Boolean ctNoInvertIfNegative = new CT_Boolean();
    ctNoInvertIfNegative.val = 0;
    ctBarSer.invertIfNegative = ctNoInvertIfNegative;

    CT_BarDir ctBarDir = ctBarChart.AddNewBarDir();
    ctBarDir.val = ST_BarDir.bar;

    CT_AxDataSource catDS = ctBarSer.AddNewCat();
    XSSFChartUtil.BuildAxDataSource(catDS, categories);
    CT_NumDataSource valueDS = ctBarSer.AddNewVal();
    XSSFChartUtil.BuildNumDataSource(valueDS, values);

    if (IsTitleSet)
    {
        ctBarSer.tx = GetCTSerTx();
    }

    if (fillColor != null)
    {
        ctBarSer.spPr = new OpenXmlFormats.Dml.Chart.CT_ShapeProperties();
        CT_SolidColorFillProperties ctSolidColorFillProperties = ctBarSer.spPr.AddNewSolidFill();
        CT_SRgbColor ctSRgbColor = ctSolidColorFillProperties.AddNewSrgbClr();
        ctSRgbColor.val = fillColor;
    }
}

in which ctGrouping.val is set to ST_BarGrouping.clustered in a hard-coded fashion.
It's the same for XSSFColumnChartData as well.

[mostmand]

I can make a pull request for that if you give me a little guide as I am not familiar with the coding conventions in this repository and the design of the chart classes. As I understood from what I saw there is an IChartDataFactory interface that is in the NPOI.Core project and I cannot create an overload for CreateColumnChartData that accepts an ST_BarGrouping argument because ST_BarGrouping is in NPOI.OpenXmlFormats.Core project that should not be referenced.

[mostmand]

I read Apache poi's source code more thoroughly and I understood that it doesn't have column chart and treats both column charts and bar charts as one with an enum to determine whether it is column or bar. Why is it two different types in NPOI?
It also has an smart enum called BarGrouping:

public enum BarGrouping {
    STANDARD(STBarGrouping.STANDARD),
    CLUSTERED(STBarGrouping.CLUSTERED),
    STACKED(STBarGrouping.STACKED),
    PERCENT_STACKED(STBarGrouping.PERCENT_STACKED);

    final STBarGrouping.Enum underlying;

    BarGrouping(STBarGrouping.Enum grouping) {
        this.underlying = grouping;
    }

    private static final HashMap<STBarGrouping.Enum, BarGrouping> reverse = new HashMap<>();
    static {
        for (BarGrouping value : values()) {
            reverse.put(value.underlying, value);
        }
    }

    static BarGrouping valueOf(STBarGrouping.Enum grouping) {
        return reverse.get(grouping);
    }
}

that maps to the underlying STBarGrouping enum.

[mostmand]

Created a PR to add support for setting Bar Grouping in column and bar charts:
#1533