a question the in Incanter google-group for a way to show the content of 2d-arrays as heatmaps.
I suggested him to use a function that takes the integer from the given coordinates and be careful about the axis-scaling. Trying it out my self it turned out to be a terrible suggestion. Sorry.
I looked into the source-code of incanter.chart/heat-map* and highjacked the place where the function was called and replaced that with the previously developed matrix-lookup. Simple and ugly.