cannot convert sptable dataframe to sf

[johnypark]

Hi @mdsumner,

Thanks for the amazing package. I am currently using it to conduct linear transform on coordinates. In the meantime, function sf does not seem to work.
Message I get:

Error in sfFromTable(x, attr_tab = attr_tab, crs = crs, ...) : 
  sf direct creation currently not available, please for now install sf and use 'library(sf); st::as_sf(sp(x, ...))'

I could convert sptable to sp and then to sf, but I just wanted to make sure that you are aware of this error.

Thanks,
John

[mdsumner]

Ah thanks yeah, sadly it's deliberate but also on the agenda to fix. Let me know about your workflows, it might help to get a better solution with the upcoming sfheaders package

[johnypark]

You're welcome @mdsumner,

One of the task led me to use spbabel was to make grid on the boundary shapefile of the region of interest.

You could make grid with sf::st_make_grid, but it does not work for tilted rectangles, since it seems to divide bounding box instead of the actual extent of the polygon.

So I did a little workaround to extract coordinates using spbabel::sptable and then did matrix transformation to put back the rectangle in the tilted position after making grid with sf::st_make_grid. sf:st_coordinates could also extract coordinates, but putting back to sf object seems to be a daunting task after matrix transformation using sf:st_coordinates, since sf offers no method to store the structure of the spatial features (maybe it's just me since I'm still in a learning phase about spatial objectives).

Anyhow, my workflow was to make grids from sf object -> sptable to extract coordinates -> matrix transformation of coordinates -> put back to sp object using sp -> convert to sf object, and if using spbabel::sf is possible then it could save me one step in my workflow. Code specified on my github (https://github.com/johnypark/TutoR_ofTheDay/blob/master/R/ShapeFileMod_2.R) if you are interested to look at.

Cheers!