R help - Feb 2006 - Heatmap.2 axes question

I'm suppressing the labeling of my rows and columns in heatmap.2 using the
commands:
 
    labRow = "  ", labCol = "  "
 
But I'd like to annotate them again using the axis command:
     axis(1, at=seq(500, 1000, 500))
     mtext("Group 1", "Group 2")       
 
For some reason however it appears that the axis command is having no
effect. My complete code is:
 
 hv <- heatmap.2(hmrf, Rowv=1:nrow(hmrf), Colv=1:ncol(hmrf), symm=TRUE,
margin=c(6, 6), trace="none", col=terrain.colors(256), 
                   main = "Heatmap: Respondent Proximities",
tracecol="red",
dendrogram="none", colsep=c(398, 811),
                   rowsep=c(398, 811), labRow = "  ", labCol = " 
")
  axis(1, at=seq(500, 1000, 500))
  mtext("Group 1", "Group 2")       
 
Note: I'm preventing re-ordering so that observations within groups are
adjacent to one another. The data is a proximity matrix produced
by random forests.
 
I suspect I'm making a simple error but not sure what it is. Any advice
would be appreciated. I'm using R 2.2.1 on a Windows XP machine.
 
Many thanks,
Joe Retzer
 

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