9:34 AM
> To: R help
> Subject: [R] Product of certain rows in a matrix without loop
>
> Hello everybody.
> Thank you again to Bert and Arun for their help on my previous
> question.
> I know have the following problem:
> I have a matrix :
> A =
> 1 2 3
> 4 5 6
Ok, here is a bandmatrix solution "by hand":
leftmatrix <- matrix( c( rep( 1, k), rep( 0, nrow(A) - k + 1)),
byrow = TRUE, ncol = nrow(A), nrow = nrow(A) - k + 1)
Gerrit
Thank you very much for your answer. Unfortunately, I cannot use any
package...
Er, ... this is qui
Thank you very much for your answer. Unfortunately, I cannot use any
package...
Er, ... this is quite unusual! (Is this is homework?)
Do you have a solution ?
Well, take a look at the resulting bandmatrix leftmatrix. Yould can
certainly build it yourself "by hand" somehow. I used the Matrix pa
Thank you very much for your answer.
Unfortunately, I cannot use any package...
Do you have a solution ?
Thank you in advance
Edouard Hardy
On Tue, Sep 3, 2013 at 11:49 AM, Gerrit Eichner <
gerrit.eich...@math.uni-giessen.de> wrote:
> Hello, Edouard,
>
> taking logs of A's elements (so that *
Hello, Edouard,
taking logs of A's elements (so that * turns into +, so to say), using a
left-multiplication with a certain band matrix of the package Matrix, and
exponentiating the result again could provide a solution (see below).
I know have the following problem:
I have a matrix :
A =
1
Hello everybody.
Thank you again to Bert and Arun for their help on my previous question.
I know have the following problem:
I have a matrix :
A =
1 2 3
4 5 6
7 8 9
9 8 7
4 5 6
3 2 1
And I would like to have :
B =
1*4*7 2*5*8 3*6*9
4*7*9 5*8*8 6*9*7
7*9*4 8*8*5 9*7*6
9*4*3 8*5*2
Gents:
The "eval(parse(...))" construction should almost always be avoided: it is
basically a misuse of R. There are exceptions, I suppose, but this does not
appear to be one of them.
Note that the use of numeric indexing does appear to be slightly faster
than logical indexing here, although I wo
18 30 20
>
> A.K.
>
> From: Edouard Hardy
> To: arun
> Cc: Bert Gunter ; R help
> Sent: Monday, September 2, 2013 11:46 AM
> Subject: Re: [R] Product of certain rows in a matrix
>
>
>
> Thank you all for your responses.
>
- Original Message -
> From: arun
> To: Bert Gunter
> Cc: R help
> Sent: Monday, September 2, 2013 11:26 AM
> Subject: Re: [R] Product of certain rows in a matrix
>
> Hi Bert,
> Thanks. It is a better solution.
>
> If nrow() is not even.
>
> Anew<- r
- 0, ] * mat1[j40 - 1, ] * mat1[j40 - 2, ] * mat1[j40 - :
NAs produced by integer overflow
5: In mat1[j40 - 0, ] * mat1[j40 - 1, ] * mat1[j40 - 2, ] * mat1[j40 - :
NAs produced by integer overflow
6: In mat1[j40 - 0, ] * mat1[j40 - 1, ] * mat1[j40 - 2, ] * mat1[j40 - :
- Original
er overflow
4: In mat1[j22 - 0, ] * mat1[j22 - 1, ] * mat1[j22 - 2, ] * mat1[j22 - :
head(res,3)
# [,1] [,2] [,3]
#[1,] NA NA NA
#[2,] NA NA NA
#[3,] NA NA NA
A.K.
From: Edouard Hardy
To: arun
Sent: Monday, September 2, 2013 2:32 PM
Subject: Re: [R] Product of certa
; #user system elapsed
> # 5.576 0.000 5.583
> dimnames(res6Alt)<- dimnames(res6New)
>
>
> all.equal(res6New,res6Alt)
> #[1] TRUE
>
>
> A.K.
>
>
>
> As you said, this is very lng.
> Do you have a better solution on big data ?
>
>
>
>
ng.
Do you have a better solution on big data ?
- Original Message -
From: arun
To: Edouard Hardy
Cc: R help ; Bert Gunter
Sent: Monday, September 2, 2013 12:07 PM
Subject: Re: [R] Product of certain rows in a matrix
Hi,
No problem.
n<- 4
t(sapply(split(as.data.frame(Anew),as.nume
rdy
To: arun
Cc: R help
Sent: Monday, September 2, 2013 11:58 AM
Subject: Re: [R] Product of certain rows in a matrix
Thank you A.K.
And do you have a solution without installing any package ?
Thank you in advance.
E.H.
Edouard Hardy
On Mon, Sep 2, 2013 at 5:56 PM, arun wrote:
>
&g
# [,1] [,2] [,3]
#1 252 640 1134
#2 18 30 20
A.K.
From: Edouard Hardy
To: arun
Cc: Bert Gunter ; R help
Sent: Monday, September 2, 2013 11:46 AM
Subject: Re: [R] Product of certain rows in a matrix
Thank you all for your responses.
The real problem i
umeric(gl(nrow(Anew),2,7))),colProds))
[,1] [,2] [,3]
1 4 10 18
2 63 64 63
3 18 10 4
4 1 3 5
A.K.
From: Bert Gunter
To: arun
Cc: R help
Sent: Monday, September 2, 2013 10:55 AM
Subject: Re: [R] Product of certain rows in a m
2] [,3]
1 4 10 18
2 63 64 63
3 18 10 4
4 1 3 5
A.K.
From: Bert Gunter
To: arun
Cc: R help
Sent: Monday, September 2, 2013 10:55 AM
Subject: Re: [R] Product of certain rows in a matrix
These elaborate manipulations are unnec
These elaborate manipulations are unnecessary and inefficient. Use indexing
instead:
j <- 2*seq_len(nrow(A)/2)
b <- A[j,]*A[j-1,]
b
[,1] [,2] [,3]
[1,]4 10 18
[2,] 63 64 63
[3,] 18 104
[,1] [,2] [,3]
[1,]4 10 18
[2,] 63 64 63
[3,] 18 104
[,1
Hi,
You could try:
A<- matrix(unlist(read.table(text="
1 2 3
4 5 6
7 8 9
9 8 7
6 5 4
3 2 1
",sep="",header=FALSE)),ncol=3,byrow=FALSE,dimnames=NULL)
library(matrixStats)
res1<-t(sapply(split(as.data.frame(A),as.numeric(gl(nrow(A),2,6))),colProds))
res1
# [,1] [,2] [,3]
#1 4 10 18
#2 6
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