# how to get the value of a pixel and its 8 surrounding pixels from points?

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## how to get the value of a pixel and its 8 surrounding pixels from points?

 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 [hidden email] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
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## Re: how to get the value of a pixel and its 8 surrounding pixels from points?

 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 > [hidden email] > https://stat.ethz.ch/mailman/listinfo/r-sig-geo_______________________________________________ R-sig-Geo mailing list [hidden email] https://stat.ethz.ch/mailman/listinfo/r-sig-geo