HI,
I just wonder whether your code worked or not.
set.seed(8)
mat1<-matrix(sample(1:80,40,replace=TRUE),ncol=8)
set.seed(25)
mat2<-matrix(sample(1:160,40,replace=TRUE),ncol=8)
#Since the dimensions are the same,
m<-1:5
n<-1:8
sum1<-0
for(i in 1:length(m)){
for(j in 1:length(n)){
sum1<-sum1+(((mat1[i,j]/d1)-(mat2[i,j]/d2))^2)
}
}
sum1
#[1] 15192.89
#Sara's code:
sum((mat1/d1 - mat2/d2)^2)
#[1] 15192.89
A.K.
----- Original Message -----
From: Charles Novaes de Santana <charles.sant...@gmail.com>
To: "r-help@r-project.org" <r-help@r-project.org>
Cc:
Sent: Tuesday, December 4, 2012 2:27 PM
Subject: Re: [R] Large loops in R
Dear Michael,
Thank you for your answer.
I have 2 matrices. Each position of the matrices is a weight. And I
need to calculate the following sum of differences:
Considering:
mat1 and mat2 - two matrices (each of them 48000 x 48000).
d1 and d2 - two constant values.
sum<-0;
for(i in 1:nrows1){
for(j in 1:nrows2){
sum<-sum+ ( ( (mat1(i,j)/d1) -
(mat2(i,j)/d2) )^2 )
}
}
}
I was wondering if there is a better way to do this sum.
Thank you for your attention!
Best,
Charles
On Tue, Dec 4, 2012 at 7:54 PM, R. Michael Weylandt
<michael.weyla...@gmail.com> <michael.weyla...@gmail.com> wrote:
>
>
> On Dec 4, 2012, at 6:47 PM, Charles Novaes de Santana
> <charles.sant...@gmail.com> wrote:
>
>> Dear all,
>>
>> I need to access data from a large matrix (48000 x 48000) and to do it
>> I am trying to run two loops using "for" command. Surely it is been a
>> very slow job.
>>
>> I heard that "for" is not the best option to perform large loops in R,
>> but I don't really know what would be the best (fast) option. sapply?
>> vapply? Could anyone help me with this issue, please?
>
> What exactly are you trying to do? It's likely doable with a few vectorized
> operations.
>
> Michael
>
>
>>
>> Thank you very much for your attention and for any help!
>>
>> Best regards,
>>
>> Charles
>>
>> --
>> Um axé! :)
>>
>> --
>> Charles Novaes de Santana
>> http://www.imedea.uib-csic.es/~charles
>> PhD student - Global Change
>> Laboratorio Internacional de Cambio Global
>> Department of Global Change Research
>> Instituto Mediterráneo de Estudios Avanzados(CSIC/UIB)
>> Calle Miquel Marques 21, 07190
>> Esporles - Islas Baleares - España
>>
>> Office phone - +34 971 610 896
>> Cell phone - +34 660 207 940
>>
>> ______________________________________________
>> 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.
--
Um axé! :)
--
Charles Novaes de Santana
http://www.imedea.uib-csic.es/~charles
PhD student - Global Change
Laboratorio Internacional de Cambio Global
Department of Global Change Research
Instituto Mediterráneo de Estudios Avanzados(CSIC/UIB)
Calle Miquel Marques 21, 07190
Esporles - Islas Baleares - España
Office phone - +34 971 610 896
Cell phone - +34 660 207 940
______________________________________________
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.
