[Gretl-devel] xls import fails - error message says expecting numerical data but found string

hi, i'm new to gretl and running into a problem importing a xls-spreadsheet: the spreadsheet has a column "sex" with values "m" or "f" and gretl throws an error telling me that she expected numerical data for this column, but found a string (which is correct, because I have values of "m" and "f". how to import this into gretl? the same error occurs when using openoffice calc. gretl 1.8.7 running on ubuntu 10.10 Marco