Display a Sparse Matrix as Color Image

The function creates a grid of colored rectangles with colors corresponding to the values of the spam matrix.

# S4 method for spam
image(x, cex = NULL, ...)

Arguments

x

matrix of class spam or spam.chol.NgPeyton.

cex

for very large matrices, the dot size may need to be scaled.

...

any other arguments passed to image.default and plot.

Details

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.

See also

display and spam.options.
The code is based on image of graphics.

Author

Reinhard Furrer

Examples

set.seed(13)

smat <- spam_random(8)

par(mfcol=c(1,2),pty='s')
options(spam.imagesize=1000)
image(smat) # or use better color schemes
options(spam.imagesize=10)
image(smat, cex=.25)


smat <- spam_random(2^14, distribution=rnorm, density=1e-5, verbose=TRUE)
#> Density is 0.0000104, specified is 0.00001 (nnz=2798).
par(mfcol=c(1,1), mai=c(.4,.4,.1,.1), pty='s')
image(smat)