[R-sig-Geo] Identify specific pixel neighbours

[Paulo Flores Ribeiro]

Thank you, Sebastiano. That worked for me.

Cheers, PauloFR


Às 06:32 de 10/11/2021, Sebastiano Trevisani escreveu:
> Hi Paulo,
>
> you could use a focal analysis approach using the "terra" package. You 
> could build for each category (e.g., "urban", "forest", etc)
> a raster with an indicator coding (1 and 0) and then apply simple 
> kernel (weight matrix, as below) doing the summation of the 
> neighboring pixels.
>
> 1 1 1
> 1 NA 1
> 1 1 1
>
> If the resulting pixel (at the center of the kernel) is >0 means that 
> one of the neighboring pixels is of the considered category.
>
> But maybe there are specialized packages doing directly this.
>
> Sincerely,
>
> Sebastiano
>
>
> /*Sebastiano Trevisani, Ph.D.*/
> /*      Associate Professor*/
> /*Applied and Environmental Geology*/
> /*
> //
> _https://orcid.org/0000-0001-8436-7798_
>
> */
> /*
> /IUAV University of Venice: //
> /*
> /www.iuav.it <http://www.iuav.it/>/
> */
> /
> *//
> Address: Dorsoduro 2206,  Venice 30123, Italy
> /Tel: +39. 041. 257 1299/
> /Mail: strevisani using iuav.it/
>
> /
> /"Le opinioni espresse sono riferibili esclusivamente all'autore e non //
> / riflettono in alcun modo una posizione ufficiale dello IUAV "/
> /
> /
> /"The views expressed are purely those of the writer and may not in any //
> /circumstances be regarded as stating an official position of the IUAV."/
> /
> /
>
>
> On Tue, Nov 9, 2021 at 6:40 PM Paulo Flores Ribeiro 
> <paulo.flores.mail using gmail.com> wrote:
>
>     I would like to create a raster from an existing one, where each
>     pixel
>     in the new raster is set to 1 if the corresponding pixel in the
>     existing
>     map is in the direct neighbourhood (8 neighbouring pixels) of at
>     least 1
>     pixel with a particular value, or 0 if otherwise (e.g., create a
>     raster
>     that identifies all "agricultural" pixels that are neighbours of
>     "urban"
>     pixels). How to do this in the most computationally efficient way?
>     Thanks in advance, PauloFR
>
>     _______________________________________________
>     R-sig-Geo mailing list
>     R-sig-Geo using r-project.org
>     https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
	[[alternative HTML version deleted]]