Count freq of multiple raster objects in R

Question

I want to write a df with the freq of 150 raster objects.

I know I can read individual raster objects with

raster_x <- raster::raster()

I can further get the freq with

raster_freq_y <- raster::freq(raster_x)

After that I can bind the freq outputs of multiple raster objects to a df with

cbind.data.frame(raster_freq_x, raster_freq_y)

What I dont know is how to do this for 150 raster objects in one go?

Should I use a loop? If so what kind of loop would make sense?

Any help is appreciated.

Robert Hijmans · Accepted Answer · 2018-09-17 14:41:31Z

1

If the RasterLayer objects have the same extent and resolution, you can combine them in a RasterStack. The below example is from ?freq

Example data:

library(raster)
r <- raster(nrow=18, ncol=36)
r[] <- runif(ncell(r))
r[1:5] <- NA
s <- stack(r, r*2, r*3)

Solution:

freq(s, merge=TRUE)

If the RasterLayer objects do not have the same extent and resolution, you can keep them together in a list and use lapply

ss <- list(r, r*2, r*3)
lapply(ss, freq)

answered Sep 17, 2018 at 14:41

Robert Hijmans

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2 Comments

loening Over a year ago

They dont have the same extent but the same resolution. Creating a list with spatial.tools::list.raster.files() and then calling lapply(ls$raster,freq) did the trick. I really have to learn more about lapply.Thank you so much!

loening Over a year ago

Maybe you can help with the second part of the question as well? <stackoverflow.com/questions/52388444/…>

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