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raster

How to make random values in a rastor?

library(terra)
y <- rast(ncol=10, nrow=10, nlyr=1, vals=rep(1, each=100))

I would like to randomly assign half of the values to NA?

Is there a way to do this?

Solution

  • To set exactly 50% of the cells to NA you could do

    library(terra)
x <- rast(ncol=10, nrow=10, nlyr=1)
x <- init(x, "cell")
x <- spatSample(x, ncell(x), "random", as.raster=TRUE)
x <- ifel(x >= ncell(x)/2, 1, NA)

    With small rasters you can also do

    y <- rast(ncol=10, nrow=10, nlyr=1, vals=1)
i <- sample(ncell(y), 0.5*ncell(y))
y[i] <- NA

    If you just wanted random values you could do

    z <- rast(ncol=10, nrow=10, nlyr=1)
z <- init(x, runif)