[R-sig-Geo] Count frequency in raster stacks

[Thiago V. dos Santos]

Hi all,

I am trying to count the frequency of values in raster objects based on specified intervals. For example, I have a raster storing monthly rainfall totals ranging from 50 to 600 mm. And I need to know how many values fall in the interval 0-100, how many on 101-200, 201-300 and so on.

I managed to do it in a single raster:

require(raster)

## scratch a raster and fill some random values
r <- raster(nrows=22, ncols=20, xmn=-58, xmx=-48, ymn=-33, ymx=-22)
r[] <- round(runif(22 * 20, min=0, max=600), digits=0)

# Count raster cells (excluding NA's) and set intervals
ncells <- sum(!is.na(r[]))
intervals <- seq(0, 600, 100)

# Count frequencies and calculate percentage
t <- table(cut(as.vector(r), intervals, include.lowest=TRUE)) / ncells * 100
df <- data.frame(round(t, digits=2))


However, how can I do the same for a raster stack, storing the count of each layer in a column of the resulting data frame? 
Thanks in advance,
 -- Thiago V. dos Santos

PhD student
Land and Atmospheric Science
University of Minnesota