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rterra

Finding cell loaction that satisfies a condition in SpatRaster

I have a multi-layer SpatRaster and would like to extract x, y, layer, and value information for cells that are greater than 200. I thought about using as.array or as.data.frame, but it will affect performance since it is a large SpatRaster.

Here is a reproducible example:

library(terra)
f <- system.file("ex/logo.tif", package="terra")
r <- rast(f, f) * * seq(1,2, by = 0.2)
Solution

  • To reduce memory needs you can first set the cells you do not want to NA, here using terra::clamp.

    x <- clamp(r, 200, values=FALSE)

d <- as.data.frame(x, xy=TRUE)
head(d)
#    x    y lyr1 lyr2 lyr3 lyr4 lyr5 lyr6
#1 0.5 76.5  255  306  357  408  459  510
#2 1.5 76.5  255  306  357  408  459  510
#3 2.5 76.5  255  306  357  408  459  510
#4 3.5 76.5  255  306  357  408  459  510
#5 4.5 76.5  255  306  357  408  459  510
#6 5.5 76.5  255  306  357  408  459  510