Thank you!
Franco
________________________________________
From: David Winsemius [[email protected]]
Sent: Thursday, September 29, 2011 8:09 AM
To: R. Michael Weylandt <[email protected]>
Cc: Mendolia, Franco; [email protected]
Subject: Re: [R] Multiplying a list of matrices with a vector
On Sep 28, 2011, at 6:26 PM, R. Michael Weylandt wrote:
> Untested:
>
> mapply('*', LL, vec)
>
> Those should be backticks but I can't type them on my phone
Actually mapply does not require backticks since it is expecting its
functions to be quoted anyway, but it didn't seem to work as you (and
I) expected.
> mapply('*', LL, vec)
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 0 0 0
[3,] 0 0 0
[4,] 0 0 0
[5,] 1 2 3
[6,] 0 0 0
[7,] 0 0 0
[8,] 0 0 0
[9,] 1 2 3
What is needed is to add SIMPLIFY=FALSE
> mapply('*', LL, vec, SIMPLIFY=FALSE)
$A
[,1] [,2] [,3]
[1,] 1 0 0
[2,] 0 1 0
[3,] 0 0 1
$B
[,1] [,2] [,3]
[1,] 2 0 0
[2,] 0 2 0
[3,] 0 0 2
$C
[,1] [,2] [,3]
[1,] 3 0 0
[2,] 0 3 0
[3,] 0 0 3
--
David.
>
> Michael
>
> On Sep 28, 2011, at 6:04 PM, "Mendolia, Franco" <[email protected]>
> wrote:
>
>> Hi all!
>>
>> I have a list of matrices and I want to multiply the ith element of
>> the list with the ith element of a another vector. That is,
>>
>>> LL <- list(A=diag(3),B=diag(3),C=diag(3))
>>> vec <- 1:3
>>> for(i in 1:3)
>> + {
>> + LL[[i]] <- LL[[i]]*vec[i]
>> + }
>>> LL
>> $A
>> [,1] [,2] [,3]
>> [1,] 1 0 0
>> [2,] 0 1 0
>> [3,] 0 0 1
>>
>> $B
>> [,1] [,2] [,3]
>> [1,] 2 0 0
>> [2,] 0 2 0
>> [3,] 0 0 2
>>
>> $C
>> [,1] [,2] [,3]
>> [1,] 3 0 0
>> [2,] 0 3 0
>> [3,] 0 0 3
>>
>> Is there another (more efficient) way of doing this without using
>> loops? I found an older entry in this list with a similar problem,
>> where the list elements were always multiplied with the same
>> number, e.g., lapply(LL, function(x) x*3) and I was looking for
>> something similar.
>>
>> Best,
>> Franco
>> ______________________________________________
>> [email protected] 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.
>
> ______________________________________________
> [email protected] 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.
David Winsemius, MD
West Hartford, CT
______________________________________________
[email protected] 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.
