I am trying to calculate incidence rate ratio for each level of an an exposure variable in Dtata, but I'm only finding that I can do it when the exposure variable has only two levels.
The exposure variable I am using is "agegroups" which has 5 levels (18-29, 30-39, 40-49, 50-59, 60+). And we are looking at time to symptom onset. I would like to use the 18-29 age category as the referent group and find incidence rate ratios for each level of the agegroup variable.
In Stata I went to Statistics > Survival analysis > Summary statistics, tests, and tables > Person-time, incidence rates, and SMR.
For the categorical variable, I chose agegroups and when I submit, I get an error message that says "variable agegroups takes on more than two values."
Is there I way I can do this calculation for agegroups ans get an IRR for each level of this categorical variable?