Round() does not return an integer raster in R

Question

I want to convert the datatype of a raster to integer. For example:

x <- raster(nrow=10,ncol=10)

its datatype is float

dataType(x)
[1] "FLT4S"

then I round the pixel values of x by

 y <- round(x)
 dataType(y)
 [1] "FLT4S"

How can I change the dataType of y to int?

Answer 1

Just tell it:

> dataType(y)="INT4S"
> dataType(y)
[1] "INT4S"

read the help for dataType to make sure you are doing the right thing though. This doesn't change R's internal storage mode:

> x=raster(nrow=10,ncol=10)
> x[]=runif(100)
> mean(x[])
[1] 0.5444336
> dataType(x)="INT4U"
> dataType(x)
[1] "INT4U"
> mean(x[])
[1] 0.5444336

If what you really meant to ask was "how do I change the underlying storage type of raster data" then possibly you can just change the storage mode of the appropriate values:

> r = raster(ncol=100,nrow=100)
> r[]=rnorm(100*100)
> object.size(r)
86460 bytes
> storage.mode(r[]) = "integer"
> object.size(r)
46460 bytes
> r[][1:10]
 [1] 0 0 -1 -1 -1 -1 0 0 -2 0

Or just coerce the values:

> r[]=rnorm(100*100)
> storage.mode(r[])
[1] "double"
> r[]=as.integer(r[])
> storage.mode(r[])
[1] "integer"

• jim: What I want is to actually change the internal storage mode so to reduce memory requirements. It is not efficient to reserve 4 bytes in memory for a pixel when 1 byte would be sufficient.
• Spacedman: Done, see edits
• ecologist1234: Hmm. When I try any of these, then import a raster saved as a .tif from R into Arcmap, I am left with a floating point raster still.
• Spacedman: How are you saving the raster? I'd guess you are not specifying datatype="INT4U" or some other integer specification in writeRaster. The default is "FLT4S".
• Spacedman: yes, and notice its datatype in writeRaster but dataType to get the type of a raster...