terra::adjacent does not include focal cell in the result

[josephlewis]

Hi @rhijmans

terra::adjacent does not include the focal cell in the returned matrix. This is true when pairs is also TRUE. See raster::adjacent for comparison

library(raster)

r <- raster::raster(nrows=10, ncols=10)
raster::adjacent(r, cells=c(1, 55), directions=8, pairs=TRUE)
raster::adjacent(r, cells=c(1, 55), directions=8, pairs=TRUE, include = TRUE)

library(terra)

r <- terra::rast(nrows=10, ncols=10)
terra::adjacent(r, cells=c(1, 55), directions=8, pairs = TRUE)
terra::adjacent(r, cells=c(1, 55), directions=8, pairs = TRUE, include = TRUE)

[rhijmans]

Thanks for reporting this. We already had

library(terra)
#terra 1.6.20
r <- rast(nrows=10, ncols=10)

adjacent(r, cells=55, directions=4, pairs=F, include=F)
#   [,1] [,2] [,3] [,4]
#54   45   54   56   65

adjacent(r, cells=55, directions=4, pairs=F, include=T)
#     [,1] [,2] [,3] [,4] [,5]
#[1,]   55   45   54   56   65

adjacent(r, cells=55, directions=4, pairs=T, include=F)
#     from to
#[1,]   55 45
#[2,]   55 54
#[3,]   55 56
#[4,]   55 65

And now this one also works as expected:

adjacent(r, cells=55, directions=4, pairs=T, include=T)
#     from to
#[1,]   55 55
#[2,]   55 45
#[3,]   55 54
#[4,]   55 56
#[5,]   55 65