Calculate mean of Var1 if X==1 minus mean of Var1 if X==2 by date

[Simon_Peters]

Hello everybody,

I asked this question in a more complicated way. So I try it in an easier way. As the title says I want to calculate:

mean of Var1 if X==1 minus mean of Var1 if X==2 by date

I would do it like that but it does not work can you help me?

by date: egen R_12=mean(Var1) if Var1==1 -(minus) mean(Var1) if Var1==2

But I do not know how I can make it work.

Hope this is a easier description.

Thanks a lot for your help

Simon

[Svend Juul]

I assume that you want a single result for each date, not multiple copies of it dispersed in the observations. Try this:

collapse (mean) meanvar1=var1 , by(date x)
reshape wide meanvar1 , i(date) j(x)
gen diffvar1 = meanvar11-meanvar12
list

[Simon_Peters]

Hello,

thanks a lot for the fast reply. It is working but then I loose data like the var "Company" and also other variables. How can I be sure that this data stays is not deleted?

thanks

Simon

[Svend Juul]

OK - you want the resulting difference to be a new variable. In that case:

sort date
by date: egen mv1_1 = mean(var1) if x==1
by date: egen mv1_2 = mean(var1) if x==2
by date: egen meanvar1_1 = mean(mv1_1)
by date: egen meanvar1_2 = mean(mv1_2)
gen diffvar1 = meanvar1_1 - meanvar1_2