Hi all:

I'm trying to estimate a simple logit model following Berry (1994)'s linearization approach to then calculate the demand elasticity based on market share. Following is the code and error I obtained and was hoping someone could offer some help to resolve the error. Many thanks.

? OWN-PRICE ELASTICITY: alpha*Pricei*(1-Sharei)
CALC ; STORE1_SH=Xbr(SHARE) $
CALC ; STORE1_PR=Xbr(PRICE) $
WALD ; FN1=B_PRICE*STORE1_PR*(1-STORE1_SH) $
Error

Error 759: Name in expr not label,variable,scalar,matrix,list,or FNi.
Error 588: Error translating function in optimization command.
Error is in 1-STORE1_SH
Error 69: WALD,NLSQ,MAXIMIZE. Cannot translate the listed string
Thanks in advance.

Best, Fred