[R-sig-Geo] how to get the value of a pixel and its 8 surrounding pixels from points?

[Bede-Fazekas Ákos]

Dear Cristabel,
function focal() of package raster is what you are searching for.
focal(x, w = matrix(1/9, ncol = 3, nrow = 3), fun = sum)
or
focal(x, w = matrix(1, ncol = 3, nrow = 3), fun = mean)

HTH,
Ákos Bede-Fazekas
Hungarian Academy of Sciences

2019.11.05. 17:10 keltezéssel, "Cristabel Durán Rangel" írta:
>
> I need to get the value of a pixel (I have coordinates for this 
> pixels) and its 8 surrounding pixel from the pixel/point. I am working 
> with NetCDF files. I am working with R.
>
> This is my code till now:
>
> nc <- nc_open(file, readunlim=FALSE)
>
> mylon <- ncvar_get(nc,"lon")
> mylat <- ncvar_get(nc,"lat")
>
> my coordinates in real-world: lat 52.5935 lon 18.4467
>
> lat.coor <-mylat[which.min(abs(mylat-52.5935))]
> lon.coor <- mylon[which.min(abs(mylon-18.4467))]
>
> var <- nc[lon.coor, lat.coor, ]
>
> In var are the values for my point. But I also need the values of the 
> 8 surrounding pixels to get an average.
>
> Thanks.
>
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo using r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo