st: problem with bootstrap in Stata 8.2

["Fabio Soares" <fvsoares@hotmail.com>]

Dear Statalisters,

I�m running a difference-in-difference propensity score program using logit 
and attnd commands and I didn�t manage to get the bootstrapped s.e. using 
the bootstrap command. Does anyone spot any mistake in the following code:

capture program drop difatt
program define difatt, rclass

use favbar9100, clear
drop if bairrinho==1 | nurb==1

xi: logit fb	dom91  agua91 esg91  lixo91  escm4_91  escm15_91  analf91 /*
                   */  menor4_91  chmul91 up1sm_91  /*
                  */  nmor91  mul91 chanalf91  amest_91  idade_91 ren_91 
i.RA

predict pscore

attnd rren_00  fb, pscore(pscore)
scalar return difren00=r(attnd)

attnd rren_91  fb, pscore(pscore)
scalar return difren91=r(attnd)

scalar return difren=r(difren00) - r(difren91)

end


bootstrap "difatt" difren=r(difren), reps(100)


Best wishes,

Fabio

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