I am trying to input files into SNPSpD which requires .pre and .map files. I hoped that, as .pre and .ped files are quite similar (as far as I know), I can just phenotype column and change file extension, but it doesn't work. I couldn't find a program that would convert file from .ped to .pre, only other way around. Does somebody have a suggestion what I could do? My .ped and .map files are in standard format for PLINK. Thank you very much.