[R] multiple values in one column

[John D. Muccigrosso]

I have some data files in which some fields have multiple values. For example

first  last   sex   major
John   Smith  M     ANTH
Jane   Doe    F     HIST,BIOL

What's the best R-like way to handle these data (Jane's major in my example), so that I can do things like summarize the other fields by them (e.g., sex by major)?

Right now I'm processing the files (in excel since they're spreadsheets) by duplicating lines with two values in the major field, eliminating one value per row. I suspect there's a nifty R way to do this.

Thanks in advance!

John Muccigrosso