[R-sig-Geo] Crossing multiple raster to obtain a list of available values for each cell - LULCC package

[Ben Tupper]

Hello,

I am unfamiliar with the LULCC package, but what you describe sounds
to me like a simple extraction at one or more cell locations. At
least, that is what I think you describe here...

> That is, if I cross three rasters of one cell, with values 0, 1, 0, I
> would like to obtain a result that would tell me that the values of that
> cell are: 0, 1, 0.

I think that is a simple matter of raster::extract().

###
library(raster)

nr <- 3
nc <- 4
ncell <- nr * nc
m <- matrix(seq_len(ncell), nc = nc, nr = nr)

one <- raster(m)
two <- raster(m * 2)
three <- raster(m * 3)

S <- stack(one, two, three)

extract(S, c(1, 3, ncell))
#      layer.1 layer.2 layer.3
# [1,]       1       2       3
# [2,]       7      14      21
# [3,]      12      24      36
###

Have I understood the issue?

Ben

On Fri, Nov 27, 2020 at 6:59 AM David García Álvarez <dagaral using ugr.es> wrote:
>
> Dear list,
>
> I want to cross multiple rasters with the same spatial resolution and
> extent and obtain as a result a summary raster or table that tells me
> which are the values that each cell acquires in the different rasters.
> That is, if I cross three rasters of one cell, with values 0, 1, 0, I
> would like to obtain a result that would tell me that the values of that
> cell are: 0, 1, 0.
>
> I have checked that the crosstab function of the raster packages allows
> to cross multiple rasters (by using a rasterstack). However, I do not
> know how to obtain the result I explained above.
>
> The LULCC package includes different functions to do that. However, in
> my experience, it is not really efficient and does not work well for
> rasters that are not very simple. The basic function of the package
> (Threemapcomparison) did not work for me or took for ages to run.
>
> Therefore, I would like to ask the community for help about: 1. ways to
> do the operation I described above, 2. to effectively work with the
> LULCC package in case I am doing something wrong or my issues with
> processing time / errors are not normal.
>
> Best,
> David
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo using r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo



-- 
Ben Tupper
Bigelow Laboratory for Ocean Science
East Boothbay, Maine
http://www.bigelow.org/
https://eco.bigelow.org