Thanks for your response.
I'm not completely sure, but is it maybe the property rapidminer.gui.plotter.matrixplot.size under Tools/Properties/Gui?
I don't think so. According to the tooltip, that property defines the size of matrix plots, in pixels.
Are you sure that "category" refers to the product of bars and stack levels? I would rather think that it refers to the number of bars and/or the number of levels.
I initially thought so too but I have seen the error message when the number of bars and the number of levels are each much lower than 200, but their product is higher than 200.
Maybe you can configure the plot differently or apply a different preprocessing on your data?
It is possible to discretize more coursely, but given my application and the number of available examples, that workaround is not ideal.
You can also try to use the Advanced Charts to create stacked bar charts in a more flexible way than with the usual Plot View.
Last time I checked, Advanced Charts were not supported by the Reporting Extension. Is this likely to change soon?
I don't know the reasons behind the limit, but would it be difficult to just push the number from 200 up to, say, 500? (Perhaps it was initially set with only normal (i.e. not stacked) bar charts in mind?)