I’ve recently been using the JFreeChart heat map node for visualising pairwise distance and linear correlations between large numbers of datasets. It works, but it’s pretty buggy and there are some useful options that could be added. This is therefore a request for a new JS-based heat map node that does more or less the same as the JFreeChart one, but is more stable and will consequently play nice in the web portal.
In terms of JFreeChart node bugs, the biggest one seems to be that the node configuration gets corrupted/lost at the drop of a hat. Opening a workflow that’s been run before often leaves the node in a semi configured state, such that attempting to rerun it will fail. It can’t even be reconfigured, as it can no longer see the input columns. The node has to be removed, re-added and configured. Copying a node from one part of the workflow to another (standard practice for me) is a no-no too. Instead of keeping the config, which may then require tweaking, it gets stuck in the semi-configured state again.
As for missing options, it would be really handy to be able to define the upper and lower bounds of the heat map. For my linear correlation map, I really want my plot to go from -1.0 to 1.0 even though the data only goes down to -0.7 or so. Also being able to define three colours, rather than just two, would be useful. Colouring my heat map so that highly -ve is blue and +ve is red, while zero is white, would certainly make it easier to interpret.
For reference, I’m running KNIME v.3.6.1 with v.3.6.0.v201805031002 of the JFreeChart plugin.
If the node could be updated and ported to JS, it would also allow for some interactivity. Being able to select and highlight sections of the map would be extremely useful for picking out hotspots.