[R] Equivalent to a BY command in SAS

[Vincent Goulet]

Le dim. 13 avr. à 22:36, zerfetzen a écrit :
>
> Hi,
> I'm very new to R and absolutely love it.  Does anyone know how to use
> something in R that functions like a BY command in SAS?
>
> For example, let's say you have a variable x, and you want to see  
> the mean.
> Easy...
>
>> mean(x)
>
> But what if you want to see the mean of x conditional on another  
> discrete
> variable?  My best attempts so far are something like...
>
>> mean(x, y_cat=1)
>
> ...which of course doesn't work.  I have downloaded plenty of R user  
> guides
> that are very informative, but am not seeing much on detailed  
> descriptives
> or data manipulation (for my life, I can't figure out how to sort an
> attached data frame, but that's another issue).  Thanks.

You didn't give much detail about what exactly you want to do (have a  
look at the Posting Guide), but... perhaps by() will do what you what.  
See ?by .

Bye!

---
   Vincent Goulet, Associate Professor
   École d'actuariat
   Université Laval, Québec
   Vincent.Goulet at act.ulaval.ca   http://vgoulet.act.ulaval.ca