title: How to put legend right next to heatmap.2 color key
body: <p>I have the following data frame:</p>
  
  <pre><code>dat &lt;- structure(list(GO = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 3L, 3L, 3L, 4L, 5L, 5L, 5L, 5L, 5L, 5L), .Label = c("apoptotic process", 
  "metabolic process", "negative regulation of apoptotic process", 
  "positive regulation of apoptotic process", "signal transduction"
  ), class = "factor"), ProbeGene = structure(c(14L, 15L, 2L, 12L, 
  7L, 11L, 16L, 8L, 19L, 13L, 3L, 1L, 18L, 4L, 10L, 5L, 9L, 17L, 
  20L, 6L), .Label = c("1416787_at Acvr1", "1418835_at Phlda1", 
  "1419282_at Ccl12", "1423240_at Src", "1424896_at Gpr85", "1434186_at Lpar4", 
  "1434670_at Kif5a", "1440374_at Pde1c", "1440681_at Chrna7", 
  "1440803_x_at Tacr3", "1442017_at LOC101056574", "1448815_at Ogg1", 
  "1448821_at Tyr", "1451338_at Nisch", "1454721_at Arel1", "1456300_at Ilvbl", 
  "1456989_at Oxgr1", "1457580_at Chd8", "1457827_at Arsj", "1460657_at Wnt10a"
  ), class = "factor"), foo = c(1.412475312, 1.413647397, 1.41297239, 
  -0.707106781, -0.707106781, -0.707106781, -0.707106781, -0.707106781, 
  -0.707106781, -0.707106781, -0.707106781, -0.707106781, -0.707106781, 
  -0.707106781, -0.707106781, -0.707106781, -0.707106781, -0.707106781, 
  -0.707106781, -0.707106781), bar = c(-0.645532476, -0.741475951, 
  -0.655185417, -0.707106781, -0.707106781, -0.707106781, -0.707106781, 
  -0.707106781, -0.707106781, -0.707106781, -0.707106781, -0.707106781, 
  -0.707106781, -0.707106781, -0.707106781, -0.707106781, -0.707106781, 
  -0.707106781, -0.707106781, -0.707106781), aux = c(-0.766942837, 
  -0.672171445, -0.757786973, 1.414213562, 1.414213562, 1.414213562, 
  1.414213562, 1.414213562, 1.414213562, 1.414213562, 1.414213562, 
  1.414213562, 1.414213562, 1.414213562, 1.414213562, 1.414213562, 
  1.414213562, 1.414213562, 1.414213562, 1.414213562)), .Names = c("GO", 
  "ProbeGene", "foo", "bar", "aux"), row.names = c(50L, 35L, 45L, 
  74L, 61L, 101L, 96L, 68L, 69L, 75L, 113L, 127L, 109L, 135L, 150L, 
  152L, 183L, 190L, 197L, 191L), class = "data.frame")
  </code></pre>
  
  <p>And with the following code:</p>
  
  <pre><code>library(gplots)
  dat.tmp &lt;- dat
  dat.tmp$GO &lt;- NULL
  rownames(dat.tmp) &lt;- dat.tmp$ProbeGene
  dat.tmp$ProbeGene &lt;- NULL
  
  pdf("output.pdf",width=10,height=20)
  heatmap.2(as.matrix(dat.tmp),margin=c(5,15),dendrogram="none",trace="none",scale="row",
            Rowv=FALSE, RowSideColors=as.character(as.numeric(dat$GO)))
  
  legend("topright",      
      legend = unique(dat$GO),
      col = unique(as.numeric(dat$GO)), 
      lty= 1,             
      lwd = 5,           
      cex=.7
      )
  dev.off()
  </code></pre>
  
  <p>I can get the following picture. 
  <img src="https://i.stack.imgur.com/ycqNK.jpg" alt="enter image description here"></p>
  
  <p>My question is how can I put the legend right next to the color key
  as shown above. Note that the size of the PDF paper is can be varied
  according to user specification. </p>
  
  <p>I guess the bottom line is I don't know how to get the exact coordinate
  for legend. Please advice.</p>