Use here package to replace setwd in all functions

[ghar1821]

We used setwd a fair bit in functions which need to reference (read or write) files, which is not great as setwd is fragile and very dependent on the way you order your files on your computer. The here package (https://here.r-lib.org/articles/here.html) can address this by making it easier to construct an OS independent path, which can then be used to to replace any setwd.

[tomashhurst]

Cool idea!