Producing heatmap using geom_raster() makes different results in PDF and display

Question

I am trying to produce heatmap using geom_raster() of ggplot2. Here is the code:

foo <- matrix(1:999,ncol=3)
ggplot(melt(foo), aes(X2,X1, fill=value)) + g         


        

Answer 1

Some pdf viewers don't manage properly the output of grid.raster, even with interpolate=FALSE they insist on showing some spurious gradient. Your pdf most probably is good (as per the pdf format specifications), it's the pdf viewer that is deficient (overzealous to smooth).

Try to see if you have some preferences in the viewer to turn off interpolation and/or a different pdf viewer, e.g. in Mac's Preview application, one can switch "smooth text and line art" off and see the expected output. There's a similar option in the cross-platform Adobe Reader.