30 Jan 1997 19:05 entrycd 7 other recoded to 1 as it is unlikely that animals were bought in much after the investigation started.
30 Jan 1997 07:49 working on the ind data for the poisson model
var age2 is the categorical var mature transformed to the age in months of the mid-period for each of the mature categories.
make a variable age3 that represents the age of the animal in days. It is necessary to do this because this is how stata looks at elapsed time.
generate exp to 1 because all of the animals in this database were exposed theoretically
To get an ir use the formula ir react_d (ie just 1 will be counted as a case) exp (ie all exposed animals) atrisk1. Specify the group that you want the ir on.