[R] levelplot/heatmap question

cerman at u.washington.edu cerman at u.washington.edu
Thu Sep 25 06:11:12 CEST 2008

I have data containing a large number of probabilities (about 60) of nonzero 
coefficients to predict 10 different independent variables (in 10 different 
BMA models). i've arranged these probabilities in a matrix like so:

  (IV1)    (IV2)    (IV3)  ...
  p(b0)    p(b0)    p(b0)
  p(b1)    p(b1)    p(b1)
  p(b2)    p(b2)    p(b2)

where p(b1) for independent variable 1 is p(b1 != 0) (given model uncertainty - 
using the BMA package). i've also set it so that if the coefficient is 
negative, the probability is listed as negative (to be able to distinguish 
between significant positive and negative effects by color).

i'd like to create a plot which is a 10x60 grid of rectangles, where each 
rectangle is colored according to its probability of being nonzero (preferably white would correspond to a zero probability). i've looked into levelplot, heatmap, and image, and cant seem to get exactly what im looking for.

heatmap gives me problems in that the output is inconsistent with the data - 
among other things, the first and last rows do not seem to show up (they are 
just white, despite clearly nonzero probabilities).  even if i do not use the 
dendrogram (Rowv and Colv set to NA), i still seem to have an issue with a 
probability in a given row not corresponding to the same color as the same 
probability in a different row.

levelplot seems to do exactly what i want it to do, except that i cant find a 
way to label the individual columns and rows, which I really need

any ideas how to obtain the graph i want?  Thanks!

-nate cermak

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