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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