Re: [R] eager to learn how to use "sapply", "lapply", ...
Have a look at the plyr package and associated documentation -
http://had.co.nz/plyr
Hadley
On Sun, Apr 26, 2009 at 12:42 PM, 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@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.
>
--
http://had.co.nz/
__
R-help@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.
Re: [R] eager to learn how to use "sapply", "lapply", ...
Also you don't need the abs since you are
squaring it anyways and seq with length
argument is a bit cleaner:
ix <- seq(Nstart, length = NW)
sum(Y[ix]^ 2)
Also please read the last line on every
message to r-help. The code in your
post lacks all 4 of the asked for
ingredients: 1. there are no comments,
2. it has lines not subsequently used
(not minimal), 3. it not self-contained
and 4. there is no reproducible
calculation.
On Sun, Apr 26, 2009 at 2:04 PM, jim holtman wrote:
> 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, 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@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?
>
> __
> R-help@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.
>
__
R-help@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.
Re: [R] eager to learn how to use "sapply", "lapply", ...
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, 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@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?
__
R-help@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.
