how does fitglm treat categorical variables?
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I'd like to verify something about categorical variables in fitglm. As input I use a table which also contains categorical variables (sex (0 vs 1), and education (on a scale 1 to 7). If I understand the documentation correctly, fitglm automatically treats these as categorical, and it also automatically dummy codes when necessary? (for education in this case). Is this correct?
Thanks very much.
Hans van der Horn
Jeff Miller on 6 Mar 2022
I don't that is correct. WIth numerical values in the table, I think you have to mark the variables as categorical with something like:
tbl.sex = categorical(tbl.sex);
tbl.education = categorical(tbl.education);
Where there are three or more categories (e.g., education) you can check the df's to make sure that the variable has been treated as categorical (6 dfs) rather than numerical (1 df, essentially a regression slope across 1-7).