[R-sig-Geo] Fill NoData cells in a raster

[Marine Regis]

Hello,



Thank you very much for your answers. To fill the noData cells, I have calculated the frequency of values of land cover types around a given noData cell and I have assigned the value of land cover type with maximum frequency to the noData cell. When there was more than one value of maximum frequency, I have used the function "sample". Here is my code with a reproducible example:



r2 <- raster(ncol=10, nrow=10) ## To check r2 <- raster(ncol=3, nrow=3)

values(r2) <- sample(1:8,ncell(r2),replace=T)

r2[c(5)] <- NA

plot(r2)

f2 <- focal(r2, w=matrix(1,nrow=3,ncol=3), fun=fillNoData, NAonly=T, pad=T)

plot(f2)



fillNoData <- function(x) {

feq_class <- as.data.frame(table(x))

colnames(feq_class) <- c("Class","Freq")

value_noData <- as.numeric(as.character(feq_class$Class[feq_class$Freq==max(feq_class$Freq)]))

value_noData <- sample(value_noData,1,replace=F)

return(value_noData)

}



Is the use of maximum frequency appropriate for filling the noData cells? In this case, when there is more than one value of maximum frequency, is it more correct to increase the moving window or to create a buffer around a given noData cell than to use the 8 neighbour cells?



Thank you very much for your time.

Marine



________________________________
De : Jefferson Ferreira-Ferreira <jecogeo at gmail.com>
Envoyé : vendredi 18 mars 2016 15:51
À : Zack Holden
Cc : Marine Regis; r-sig-geo at r-project.org
Objet : Re: [R-sig-Geo] Fill NoData cells in a raster

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2016-03-18 10:45 GMT-04:00 Zack Holden <zaholdenfs at gmail.com<mailto:zaholdenfs at gmail.com>>:
Marine,
The focal() function in the raster library should work. You should be able
to apply a custom function to only NA cells by setting NAonly=T.

require(raster)
?focal

Zack


On Thu, Mar 17, 2016 at 5:27 PM, Marine Regis <marine.regis at hotmail.fr<mailto:marine.regis at hotmail.fr>>
wrote:

> Hello,
>
> I am beginner in spatial statistics and I would need some advice. I have a
> raster that is based on a grid of 30 m resolution and in which each cell is
> assigned to one of ten land cover types (coded as 1, 2, 3, 4, ..., 10 in
> the raster). However, there are some NoData cells in the raster. Is there
> an efficient way to fill NoData cells with reasonable values of land cover
> types? Should I use an interpolation method?
>
> Thank you very much for your time.
>
> Marine
>
>
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Jefferson Ferreira-Ferreira

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