This function exports the R matrix data in 'GGUM2004'
(Roberts, Donoghue, & Laughlin, 2000; Roberts et al., 2006) friendly
format. This data file is to be used together with a 'GGUM2004' command
script (or using the GUI itself, of course). 'GGUM2004' may be executed
directly or may be called from R, see run.GGUM2004.
By experience, we noticed that long directory paths (especially if spaces
are included) make 'GGUM2004' fail to execute with error
file not found. Therefore, a good advice is to choose
data.dir wisely (short paths, no spaces).
Observe that this function is optimized for the Windows operating system
because 'GGUM2004' is a Windows program.