checkPlink checks that the PLINK software (https://www.cog-genomics.org/plink/1.9/) can be found from system call.
checkPlink(path2plink = NULL)
[character] Absolute path to PLINK executable
(https://www.cog-genomics.org/plink/1.9/) i.e.
plink should be accessible as path2plink -h. The full name of the executable
should be specified: for windows OS, this means path/plink.exe, for unix
platforms this is path/plink. If not provided, assumed that PATH set-up works
and PLINK will be found by exec
('plink').
Path to PLINK executable.