non-portable filename construction

[mrd]

https://github.com/Spatial-Data-Science-and-GEO-AI-Lab/GreenExp_R/blob/7a52a5d6615088e50a4ba11ee25524cadab8b46d/R/green_cover.R#L301

Note that constructing pathnames with string concatenation like this can cause problems on systems that don't use forward slash as directory separator. Although these days that is mostly just Windows & probably R handles that for you. But just be aware.

There's a 'proper' way to do it: https://stat.ethz.ch/R-manual/R-devel/library/base/html/file.path.html

I picked this example for the bug report, but like the other reports, there are multiple instances of this problem, I will only report one though.