[R] Calculate focal values for neighboring cells that are located at the raster edge from the function "focal" in the R package "raster"
Jeremie Juste
jerem|eju@te @end|ng |rom gm@||@com
Sat Jun 9 14:25:18 CEST 2018
Hello,
>> I am using the function "focal" in the R package "raster" but I don’t
>> understand how the function calculates values for neighboring cells that
>> are located at the raster edge. Here is an example reproducible:
focal is a method for the S4 object RasterLayer. You can have access to
this method by using
> findMethods("focal")
and you can trace the method by using
> trace(what='focal', tracer=browser, at=1, signature='RasterLayer')
HTH,
Jeremie
>> }
>>
>> r <- raster(ncol=3, nrow=3)
>> vals <- 1:ncell(r)
>> r <- setValues(r, vals)
>> plot(r)
>>
>> func_f <- focal(r, w=matrix(1,nrow=3,ncol=3),
>> fun= func, pad = TRUE, padValue = NA)
>> text(func_f )
>> getValues(func_f)
>>
>>
>> From the example, I manage to find the value “2.06066”:
>>
>> c <- 5
>>
>> (abs(1-c)*(1/sqrt(2)) + abs(2-c)*1 + abs(3-c)*(1/sqrt(2)) +
>>
>> abs(4-c)*1 + abs(5-c)*0 + abs(6-c)*1 +
>>
>> abs(7-c)*(1/sqrt(2)) + abs(8-c)*1 + abs(9-c)*(1/sqrt(2))) / 8
>>
>>
>> but I don’t manage to find the value “2.18566”. How can I find this value
>> ? In addition, why does the function with “pad = TRUE” and without
>> “pad=TRUE” give the same result ?
>>
>> Thank you very much for your time.
>>
>> Have a nice day
>>
>> Marine
>>
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code. Is
>> helpful is
>>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
More information about the R-help
mailing list