[R] image 256 x 920 data points too slow

[Katharine Mullen]

I'm not aware of any existing function that does what you want, but you
could easily write a function to sample from x, y, z, and then pass the
sampled values to image. e.g.,

sam <- function(sx,sy,x,y,z){
  xind<-seq(1,length(x),by=sx)
  yind<-seq(1,length(y),by=sy)
  samplex<-x[xind]
  sampley<-y[yind]
  samplez<-z[xind,yind]
  list(x=samplex,y=sampley,z=samplez)
}
newval<-sam(sx=13.3,sy=15,x=x,y=y,z=z)
image(newval$x,newval$y,newval$z)

On Sun, 21 Oct 2007, [ISO-8859-1] baptiste Auguié wrote:

> Dear R gurus,
>
> I'm trying to visualize a matrix 256 x 920 using image(), but i find
> the display too slow (~ 1 minute –– admittedly, my iBook G4 isn't
> very fast). The aim is not to get a good resolution image, but rather
> have a quick look at the matrix. I couldn't find a way to plot a
> smaller set of points from my data in a sensible manner (basically, i
> want to decrease the resolution). Is there an easy option for this
> purpose in image(), or possibly the lattice equivalent?
>
> Minimal example:
>
> x<-c(1:256)
> y<-c(1:920)
> z<-x%*%t(y)
> image(x,y,z)
>
>
> Best regards,
>
> baptiste
>
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