PLINK Dosage file without family ID error

Question

[Stover]

Hi,

I am simply trying to extract a small set of SNPs from a .dos dosage file using plink1.9. However, I get the error:

Line 1 of yourfile.dos has fewer tokens than expected

I have checked that the .fam file and the .dos file have the same number of individuals. Now, my .dos file does not contain any columns for family ID dosages, so I suspect this is why I'm getting the error. Perhaps plink is expecting twice the number of columns. Does anybody know how to remedy this sort of issue?

I have to use plink1.9 for this task, so I can't simply use another program. I also cannot edit each .dos file manually, as they are too large.

Thanks.