Feature request: strict implementation of extract(<SpatRaster>, <polygons>, touches = FALSE)

[florisvdh]

With regard to terra::extract() I now understand (from https://stackoverflow.com/a/67666183):

Note that terra also returns a value for a polygon that does not cover any cell center. In effect the option touches=TRUE is always used for such polygons to avoid returning NA.

I have a use case where I need to extract cell values for the polygons that effectively intersect with cell centers, returning NA when a polygon is not intersecting cell centers.

• I think this cannot currently be done with terra::extract()?
• I'd be happy to see the small = FALSE argument of raster::extract() – or some equivalent implementation – appear in terra::extract().

Actually I'm in doubt whether the default approach – to mix touches = FALSE for polygons that intersect cell centers and touches = TRUE for polygons that don't intersect cell centers – matches the user's expectation of terra::extract(x, y, touches = FALSE). At least it is not documented in ?terra::extract that a hybrid approach is implemented.

An alternative to adding a small argument could be to distinguish a third value touches = "hybrid" to reflect current behaviour instead of FALSE, but then having a strict implementation of touches = FALSE would be a breaking change.

[rhijmans]

Thanks. That was indeed a bit loose. I have opted for adding argument "small=TRUE".

[florisvdh]

Thanks; the updated package does this well 👍.