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

[Roger Bivand]

On Fri, 24 Aug 2018, nevil amos wrote:

> Thanks,
>
> I think it did help
> datatype vs dataType was indeed the problem!

The underlying problem is that dataType= is going into ..., and because 
nothing needs it, it isn't spotted. Could someone contribute a PR to trap 
this, from https://github.com/rspatial/raster?

Roger

>
> On Fri, 24 Aug 2018 at 22:14, Michael Sumner <mdsumner using gmail.com> wrote:
>
>> That doesn't help though!
>>
>> Sorry, I thought that was it, will sleep on it.
>>
>> Cheers, Mike
>>
>> On Fri, 24 Aug 2018 at 22:00 Michael Sumner <mdsumner using gmail.com> wrote:
>>
>>> 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
>>>>> 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
>>>
>>> --
>> Dr. Michael Sumner
>> Software and Database Engineer
>> Australian Antarctic Division
>> 203 Channel Highway
>> Kingston Tasmania 7050 Australia
>>
>>
>

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: Roger.Bivand using nhh.no
http://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en