[R-sig-Geo] Problems converting rasters from float to integer.

[Michael Sumner]

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 using 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 using 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 using 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 using r-project.org >
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Dr. Michael Sumner
>> Software and Database Engineer Australian Antarctic Division 203 Channel
>> Highway Kingston Tasmania 7050 Australia
>> <https://maps.google.com/?q=203+Channel%0D%0A+Highway+Kingston+Tasmania+7050+Australia&entry=gmail&source=g>
>> [[alternative HTML version deleted]]
>> _______________________________________________ R-sig-Geo mailing list
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>> --
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

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