Question

The piece of code given below will read and show image of the file with a legend.
how can I tell R to not take into consideration the values of ,for example -9999 ,or any other values when drawing legend.

conne <- file("C:\\DEM.bin", "rb")
image(t(t(y)),ylim=c(1,0))
image.plot(t(t(y)), add = FALSE, legend.shrink = 0.9,legend.width = 1.2,
           legend.mar = NULL, graphics.reset = FALSE, horizontal = FALSE, bigplot = NULL,
           smallplot = NULL,legend.only = FALSE,lab.breaks=NULL, axis.args=NULL))

Answer 1

Let’s create a mockup dataset (your dataset is not reproducible):

m = matrix(runif(100), 10, 10)
m[sample(1:10, size = 2), sample(1:10, size = 2)] = -9999

matrix m now contains two values you do not want to plot:

The solution is to make them NA, in which case R will know they are missing values:

m[m == -9999] <- NA
image(m)

The NA values are now ignored, and replaced by white pixels, and your image looks normal. If there are multiple values you want to make NA:

m[m %in% c(-9999, 1e30, -1)] <- NA

now all the values in the list are marked as NA.