Sorry for the silly question.
 
I am trying to perform a simple operation on a subsample of my data
loaded as data and attached:
 
data<-read.dta(name file)
attach(data)
 
Say x=1,2 and y=4,5 I want to summarize z only if x=1 & y=4. I thought
that the way to do that would be to 
write if((x=1) & (y=4)) summary(z)
butwhen I do this the result I get is for the whole data (irrespective
of the conditions imposed). Can anyone help?
 
 
Thanks
Giacomo

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