Problems converting rasters from float to integer.

Sorry, I was wrong - the actual issue is that the writeRaster argument is
"datatype", it gets conflated with the function that is dataType().

f <- "test_int.tif"
writeRaster(r, f, datatype = "INT2U", overwrite = TRUE)
s <- raster(f)
dataType(s)

[1] "INT2U"

Not the first time this has caught me out. I found it by checking
mode(readGDAL(f)[[1]]) and realizing that the TIFF type was Float32, prior
to the next steps.

HTH

:)

Cheers, Mike

On Fri, 24 Aug 2018 at 18:26 nevil amos <nevil.amos at gmail.com> wrote:

Roger,

there was a reproducible example in my post:  it seems to have got a bit
scrambled in your reply.

from the help in raster I thought that if I included  datatype="INT2S" in
the writeRaster() command the values would be formatted in the output file
( and the subsequent reading using raster() of that file) as integer  is
this not the case?

Here it is the reproducible example

v<-c(rep(1.00000,25),rep(0.00000,50),rep(NA,25))
m<-matrix(v,10,10)
r<-raster(m)
dataType(r)
writeRaster(r,"test_int.tif",dataType="INT2U",overwrite=T)
s<-raster("test_int.tif")
dataType(s)

On Fri, 24 Aug 2018 at 18:05, Roger Bivand <Roger.Bivand at nhh.no> wrote:

Thanks, Mike. I agree that the lower level interface in rgdal is
flexible enough, but as you say non-trivial. Nevil: could you please
provide a small reproducible example to point people in the right direction?

Roger

Roger Bivand
Norwegian School of Economics
Bergen, Norway



Fra: Michael Sumner
Sendt: fredag 24. august, 09.14
Emne: Re: [R-sig-Geo] Problems converting rasters from float to integer.
Til: nevil amos
Kopi: r-sig-geo at r-project.org


I'm pretty sure readGDAL from rgdal (that raster uses) will keep as
integers, so you can build an empty raster and copy the values over. But
will need to derive from the rgdal version to catch all the metadata
(structure, extent, and crs). I think it's doable and will try later. There
are other options but nothing trivial afaik. Cheers, Mike On Fri, 24 Aug
2018, 16:45 nevil amos wrote: > I have a large number of rasters ( tiffs)
that contain whole number values > between 0 and 100, and NA values. or
0,1,and NA > they are currently in Float format, I am trying to rewrite
them as integer > rasters, firstly to save space, and secondly so that I
can later read the > values stack of all the rasters into an integer array.
using getValues(). > > To do this I am setting the dataType to INT2U in
writeRaster, however when > I read the save file back into R the format is
not INT2U but FLT8S > > toy example: > > v m r dataType(r) >
writeRaster(r,"test_int.tif",dataType="INT2U",overwrite=T) > s dataType(s)

the result I get: > > > v > m > r > dataType(r) > [1] "FLT4S" > >

writeRaster(r,"test_int.tif",dataType="INT2U",overwrite=T) > > s >
dataType(s) > [1] "FLT8S" > > > > > Can you suggest how I ensure the values
are stored as integer? > > Many thanks > > [[alternative HTML version
deleted]] > > _______________________________________________ > R-sig-Geo
mailing list > R-sig-Geo at r-project.org >

Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

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