

Hello,

Below a modified function for displaying a correlation matrix by Vincent
Zoonekynd posted in his excellent tutorial. Compared to the matrix and the
legend, the colouring of the polygons is wrong. The error is in the
sequence: col=col[N*(mat[i,j]+1)/2].

I cannot seem to devise a sequence which will make the colouring consistent
with that in the legend. Can you help? The number of different colours is
given by the parameter "dens".

Thanks,
Serguei Kaniovski

#--FUNC. CORR. PLOT
cor.plot<-function(mat, dens, ticks, main="") {
 n<-dim(mat)[1]
 m<-dim(mat)[2]
 N<-ifelse(dens>10,10,dens)

   col=gray(1:N/N)
 plot(NA, xlim=c(-0.1,1.3), ylim=c(-1,0.1), axes=0, xlab="", ylab="",
 main=main)

 #POLYGONS
 for (i in 1:n) {
  for (j in 1:m) {
   polygon(c((j-1)/m,(j-1)/m,j/m,j/m), -c((i-1)/m, i/m, i/m, (i-1)/m),
   col=col[N*(mat[i,j]+1)/2])
  }
 }

 #TICKS
 text(seq(1/(2*n),1-1/(2*n),1/n), rep(0,n), toupper(substr(ticks,1,2)),
 pos=3)
 text(rep(0,m), seq(-1/(2*m),-1+1/(2*m),-1/m), toupper(substr(ticks,1,2)),
 pos=2)

 #LEGEND
 for (i in 1:N) {
  polygon(c(1.1,1.1,1.2,1.2), -c((i-1)/N, i/N, i/N, (i-1)/N),
 col=col[N-i+1])
 }

 text(rep(1.2,N+1), -N:0/N, -(N/2):(N/2)/(N/2), pos=4)
}

options(digits=2)

#--NAMES
namjid<-c("mike", "tommy", "clara", "silvio", "jimmy", "jeffrey", "carl",
"randy", "tara")
njid<-length(namjid)

#--CORRELATION MATRIX
corrmat<-diag(rep(0.5,njid))
corrmat[lower.tri(corrmat,diag=0)]<-runif(choose(njid,2),-1,1)
corrmat<-corrmat1+t(corrmat)

#--CALL
cor.plot(mat=corrmat, dens=4, ticks=namjid, main="")
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