I quite like generating plots in KNIME using R and ggplot2. I don't think we have anything for treemaps, but if you send me an example of what you are going for, I can try to figure something out.
If you are looking something similar to this, the vega integration can be changed to handle similar data with for example xml columns, though I'll have to think about more how to do it (though do not hold your breadth till it is ready, the soonest option to be done is during early 2014).
I looked into this and it turned out to be pretty easy. There is a nice treemap package in R called ... treemap. This plays very nicely in terms of expected data structure with our GroupBy node. Have a look at the attached example. The relevant R code looks something like:
Where Country, Region, and City are columns that have been aggregated, and Size is the column which contains the aggregated data (in this case, webform submission counts).
Thank you for your example workflow. At the moment the update sites with the new node libraries are not available - I am not sure if this is my problem or a general problem. I will test it as soon as possible. I use the R integration in the "R directory directy below the root of the node repository.
Your treemap is one solution for my problem. In the meantime I found another possible solution. See the example workflow under classification learner .
This is an interesting webpage with examples of data visualisation: http://flowingdata.com/.
And there is another page with examples: http://www.ct.de/1317110 (But it is only in German and the corresponding article is puslished in the German ct Magazin 17/2013).
I set the path to the R home (1.14.2) in the preferences menu, installed the package treemap and I tested your treemap workflow, but got this error message:
There is a bit of jiggling you have to do the get the R nodes working sometimes depending on your setup. Have a look at the FAQ entry below and let us know if that helps.