[R] eager to learn how to use "sapply", "lapply", ...

[jim holtman]

I think you can replace your 'for' loop with vectorized operations:

  if(NW > 0){
      Rnorm <- Rnorm + sum(abs(Y[Nstart:(Nstart + NW - 1)])  ^ 2)
    }

On Sun, Apr 26, 2009 at 1:42 PM,  <mauede at alice.it> wrote:
> After a year my R programming style is still very "C like".
> I am still writing a lot of "for loops" and finding it difficult to recognize where, in place of loops, I could just do the
> same with one line of code, using "sapply", "lapply", or the like.
> On-line examples for such high level function do not help me.
> Even if, sooner or later, I am getting my R scripts to do what I expect, I would really like to shake my C programming style off.
> I am staring at my R script and thinking "how can I improve it ?"
> For instance, I have a lot of loops similar to the following one and wonder whether I can replace them with a proper call to a high level R function that does the same:
>
>    Nstart <- Nfour/(2^Lev) + 1
>     Nfinish <- Nstart -1 + Nfour/(2^Lev)
>     LengLev <- Nfinish - Nstart + 1
>     NW <- floor(LengLev*N/Nfour)
>     if(NW > 0){
>       for(j in Nstart:(Nstart + NW -1)){
>          Dw <- abs(Y[j])
>          Rnorm <- Rnorm + Dw^2
>       }
>     }
>
>
> Thank you very much for helping me get better.
> Maura
>
>
>
>
>
> tutti i telefonini TIM!
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?