image {spam} | R Documentation |
The function creates a grid of colored rectangles with
colors corresponding to the values in z
.
## S4 method for signature 'spam' image(x, cex = NULL, ...)
x |
matrix of class |
cex |
for very large matrices, the dot size may need to be scaled. |
... |
any other arguments passed
to |
getOption("spam.imagesize")
determines if the sparse matrix is
coerced into a matrix and the plotted similarly to image.default
or if
the matrix is simply represented as a scatterplot with
pch="."
. The points are scaled according to
cex*getOption("spam.cex")/(nrow+ncol)
.
For some devices or for non-square matrices,
cex
needs probably some adjustment.
The a zero matrix in spam
format has as (1,1) entry the value
zero and only missing entries are interpreted as NA
in the
scatter plot.
Reinhard Furrer
display
and spam.options
.
The code is based on image
of graphics
.
set.seed(13) nz <- 8 ln <- nz smat <- spam(0, ln, ln) smat[ cbind(sample(ln,nz), sample(ln,nz))] <- 1:nz par(mfcol=c(1,2),pty='s') options(spam.imagesize=1000) image(smat) # better: col=tim.colors(nz)) options(spam.imagesize=10) image(smat) # better: col=tim.colors(nz)) nz <- 128 ln <- nz^2 smat <- spam(0,ln,ln) smat[cbind(sample(ln,nz), sample(ln,nz))] <- 1:nz par(mfcol=c(1,1), pty='s') image(smat,cex=100) # better:, col=tim.colors(nz))