I am using Stata 15.1 for Mac. My dataset after 1:4 case:control matching has 1168 cases (patients with brain tumors) and 4681 controls (patients without brain tumors). Each matched set (1 case and 4 controls) have the same group id which I named pairid. I matched on gender, race, smoking history.
pairid tumor tumortype
1 no non
1 no non
1 no non
1 no non
1 yes primary
2 no non
2 no non
2 no non
2 no non
2 yes metastatic
pairid range is from 1 to 1174
From this main dataset, I would like to analyze the subset of only primary tumors with their matched non tumor controls. There are 825 primary tumors. Primary tumors are coded 0, metastatic tumors are coded 1.
When I run commands such as
. graph box age if tumortype==0, over(tumor)
I wanted to see two boxes, one for tumor (in this case primary only) and one for their matched non tumors. In reality, I only see one box labeled tumor.
or
. clogit tumor age if tumortype==0, group(pairid)
yields: outcome does not vary in any group
or
. by tumortype, sort : clogit tumor age, group(pairid)
yields: -> tumortype = primary
outcome does not vary in any group

Any help would be appreciated.
Thanks
Richard