R help - Sep 2012 - equivalent of Stata "by construct"

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?




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This communication is for informational purposes only. I...{{dropped:29}}

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

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
> On Behalf Of Pradipto Banerjee
> Sent: Thursday, September 27, 2012 9:13 AM
> To: r-help at r-project.org
> Subject: [R] equivalent of Stata "by construct"
> 
> 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?
> 
> 
> 
Check out the function by() in base R.

Dan

Daniel Nordlund
Bothell, WA USA