Get raster cell coordinates using the 'calc' function in R

Question

I am trying to run a 'calc' function in R and I can't seem to find a way to obtain the coordinates of the cell that is being processed. What I'm trying to do is simple : Using the 'calc' function on a binary raster (0 and 1)-- If the raster value is '0', then change to 'NA'. If the raster value is '1', then apply a series of processes for which I will need to cell coordinates to be stored into variables.

processAllCells = function(cell) {
  if (cell == 0) {
    cell = NA
    return(cell) 
  }
  else {
    cellCoords = coordinates(cell) ### This is what I'm trying to do. This does not work. See the error message.
    ### Here will go further processes using the cell coordinates.
    return(cell)
  }
}

outputRaster = calc(lake, processAllCells)

Error message :

Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘coordinates’ for signature ‘"integer"’
In addition: Warning message:
In if (cell == 0) { :

 Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘coordinates’ for signature ‘"integer"’

Thanks everyone!

Are you importing coordinates function from some library or did you write it yourself? — eonurk
The function takes an object to calculate the coordinates, not an integer or vector of integers. That might be the problem you are experiencing. — eonurk
Yes, that is exactly the problem. The variable 'cell' only contains its value, so '1'. But I was wondering if anyone had an idea as to how I could get its coordinates. — Antoine Prince

Robert Hijmans Robert Hijmans · Accepted Answer · 2020-03-19T03:46:33

That is not possible. But you can make a RasterLayer with the x and y coordinates and used these in calc.

library(raster)
r <- raster(nrow=10, ncol=10, values=1:100)
x <- init(r, "x")
y <- init(r, "y")

And then

s <- stack(r, x, y)
#x <- calc(s, your-function)

Get raster cell coordinates using the 'calc' function in R

1 Answers