equivalent of Stata "by construct"
On 27/09/2012 12:13 PM, Pradipto Banerjee wrote:
I am evaluating a switch from Stata to R. I don't need to extensive Statistical methods, but the main reason I am exploring the switch is the coding flexibility in R (e.g. Stata does not support linear/quadratic programming). I have been going over the R syntax and I had a quick question: In Stata, one has a very useful construction called "by", e.g. by month signal: gen xxx = myfunction(yyy zzz) if cond1==cond2 Similarly, in SAS, one can write by monthn signal; if cond1=cond2 then xxx = myfunction(yyy zzz); run; I looked at a lot of R tutorials, but I haven't come across the equivalent of the Stata or SAS "by" construct in R?
There's a by() function, and also the more general tapply(). There are also contributed packages with related functions, e.g. the sparseby() function in the reshape package. I believe the reshape2 package has the same functionality, but I forget what function does it. Duncan Murdoch