as.im in spatstat::ppm not working as before

r.grid.world.SGDF.F[[1]] is a numerical vector, not even a matrix, so 
clearly as.im.default doesn't know what it should do with it.

Maybe there was once a method as.im for r.grid.world.SGDF.F, which is of 
class SpatialGridDataFrame, but no longer - software evolves.

A way you could approach this is converting that object to a stars object:

 > library(stars)
Loading required package: abind
Loading required package: sf
Linking to GEOS 3.12.1, GDAL 3.8.4, PROJ 9.3.1; sf_use_s2() is TRUE
 > as.im(st_as_stars(r.grid.world.SGDF.F))
Error: Only projected coordinates may be converted to spatstat class objects

and that points you to another issue you have: spatstat works with data 
in Cartesian coordiantes (R2), not with geodetic coordinates (S2). So 
that's a helpful error message.

Dear Members,

I'll calculate some old codes for a paper review, and I'm astonished that as.im() for fitting the Poisson model is not working as before. In my example:

library(raster)
library(spatstat)


# Elevation
r.grid.world <- raster('https://raw.githubusercontent.com/Leprechault/trash/main/wc2.1_10m_elev.tif')
proj4string(r.grid.world) <- CRS("+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0")
r.grid.world.SGDF.F <- as(r.grid.world, "SpatialGridDataFrame")


#Fitting Poisson model
fit.c <- ppm(nztrees, ~ elev,
covariates=list(elev=as.im(r.grid.world.SGDF.F[[1]])))
#
# Error in as.im.default(r.grid.world.SGDF.F[[1]]) :
# ? Can't convert X to a pixel image

I tried as matrix and rotate, and the final real-valued pixel image didn't work as a covariate in the model.

Please, any help with it?

Thanks in advance

Alexandre

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