st: Margins error

[Issa Kohler-Hausmann <ikh210@nyu.edu>]

Hello - 

I am sorry if this is a dumb question but I have having trouble with the "margins" command after running a logistic regression and I cannot figure out what I am misunderstanding. 

I am trying to graph the effect of the number of misdemeanor convictions (p_misdcon_cat) on the likelihood of conviction to a misdemeanor crime (outcome --> convict_Misd). The problem (it seems to me) is that STATA does not recognize the variables for purposes of the margins command that were generated using xi. logit and I don't know any other way of doing this. It also seems from all of the examples online that this should work. 

I ran the following logic model:

. xi: logit convict_Misd i.race_eth_cat male p_felcon i.p_misdcon_cat arrestnum_cat MisdArr, cluster(my_case_id)

I then get the following errors when I try the margins command evaluated at specified levels of my covariates. 

. margins, dydx(p_misdcon_cat) at (_Irace_eth__2=1 male=1 p_felcon=0 arrestnum_cat=4 MisdArr=1)
'p_misdcon_cat' not found in list of covariates
r(322);

. 
. margins p_misdcon_cat, at (_Irace_eth__2=1 male=1 p_felcon=0 arrestnum_cat=4 MisdArr=1)
'p_misdcon_cat' not found in list of covariates
r(322);

Any help would be greatly appreciated!

Thank you



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