@WendyCzika wrote: Yes, I think you need to change the '?'s to '.'s for the missing values. The '?' makes it think those columns are character instead of numeric, so that's why it will only allow the level to be nominal. Hope that helps (and let me know if that doesn't work). Thank you very much for the tip, it worked! I had to edit the file manually entry-by-entry, because in Excel when I tried to make the replace function (the one next to search) substitute the "?"s with "."s, the program replaced every character of every cell with ".". I was lucky the missing values were just ~20 and the dataset was small, so there was only a little manual work, but I wonder how to replace automatically in .csv files with Excel.
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