Re: [R] How to repeat vectors ?
Hi, Thanks you guys for all the help. I learned a lot from it. It looks using apply() is not an efficient way, since all it does is looping through each row(or col) , which would be slow for large matrix, right ? cheers - Original Message - From: Gabor Grothendieck [EMAIL PROTECTED] Date: Saturday, September 30, 2006 4:54 am Subject: Re: [R] How to repeat vectors ? To: Tong Wang [EMAIL PROTECTED] Cc: r-help@stat.math.ethz.ch Here are 4 approaches in order from most compact to least. #1 only works for numeric matrices, # 2 is a shorter versio of your solution using rep.vec and # 3 is from Alex's post and is likely what I would use in practice. m - matrix(1:4, 2) # test matrix # 1 - m must be numeric for this one to work kronecker(m, rep(1,2)) # 2 apply(m, 2, rep, each = 2) # 2 # 3 - from Alex's post m[rep(1:nrow(m), each = 2),] # 4 matrix(rbind(c(m), c(m)), nc = ncol(m)) On 9/30/06, Tong Wang [EMAIL PROTECTED] wrote: I just figured out a way to do this: rep.vec - function(X,n) return(t(array(rep(X,n),c(length(X),n Then,apply(MyMatrix, 2, rep.vec,2) Is there a better way ? Is there an internal function to repeat a vector or matrix ? Thanks a lot. - Original Message - From: Tong Wang [EMAIL PROTECTED] Date: Friday, September 29, 2006 11:23 pm Subject: How to repeat vectors ? To: r-help@stat.math.ethz.ch Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best __ R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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] How to repeat vectors ?
Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best __ R-help@stat.math.ethz.ch 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] How to repeat vectors ?
I just figured out a way to do this: rep.vec - function(X,n)return(t(array(rep(X,n),c(length(X),n Then,apply(MyMatrix, 2, rep.vec,2) Is there a better way ? Is there an internal function to repeat a vector or matrix ? Thanks a lot. - Original Message - From: Tong Wang [EMAIL PROTECTED] Date: Friday, September 29, 2006 11:23 pm Subject: How to repeat vectors ? To: r-help@stat.math.ethz.ch Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best __ R-help@stat.math.ethz.ch 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] How to repeat vectors ?
Solution: m[rep(1:nrow(m),each=2),] Explanation: There is a simple and effective way to do this, using array slices. for your input matrix, m: m=matrix(paste(a,c(11,12,21,22),sep=),2) m [,1] [,2] [1,] a11 a21 [2,] a12 a22 you want to create [,1] [,2] [1,] a11 a21 [2,] a11 a21 [3,] a12 a22 [3,] a12 a22 First, let's just consider the simpler problem of vectors - taking the first column as an example: v=m[,1] v [1] a11 a12 and you want: [1] a11 a11 a12 a12 which is the first element, followed by another copy of the first, and then the second, followed by another copy of the second, ie: v[c(1,1,2,2)] [1] a11 a11 a12 a12 can we generate the sequence c(1,1,2,2) automatically? yes: rep(c(1,2),each=2) [1] 1 1 2 2 or: rep(1:length(v),each=2) [1] 1 1 2 2 So let's apply that to the vector: v[rep(1:length(v),each=2)] [1] a11 a11 a12 a12 Going back to the matrix, we can see that we want to do the same thing, but to the rows of the matrix, instead of the elements of the vector: Instead of length, we use nrow, and we use the row specifier [r,] m[rep(1:nrow(m),each=2),] [,1] [,2] [1,] a11 a21 [2,] a11 a21 [3,] a12 a22 [4,] a12 a22 -Alex On 30 Sep 2006, at 07:33, Tong Wang wrote: I just figured out a way to do this: rep.vec - function(X,n)return(t(array(rep(X,n),c (length(X),n Then,apply(MyMatrix, 2, rep.vec,2) Is there a better way ? Is there an internal function to repeat a vector or matrix ? Thanks a lot. - Original Message - From: Tong Wang [EMAIL PROTECTED] Date: Friday, September 29, 2006 11:23 pm Subject: How to repeat vectors ? To: r-help@stat.math.ethz.ch Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best __ R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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] How to repeat vectors ?
Maybe this one? MyMatrix - matrix(1:4, nrow=2) MyMatrix [,1] [,2] [1,]13 [2,]24 MyMatrix[rep(seq(nrow(MyMatrix)), each=2), ] [,1] [,2] [1,]13 [2,]13 [3,]24 [4,]24 HTH, Adrian On Saturday 30 September 2006 09:33, Tong Wang wrote: I just figured out a way to do this: rep.vec - function(X,n) return(t(array(rep(X,n),c(length(X),n Then,apply(MyMatrix, 2, rep.vec,2) Is there a better way ? Is there an internal function to repeat a vector or matrix ? Thanks a lot. - Original Message - From: Tong Wang [EMAIL PROTECTED] Date: Friday, September 29, 2006 11:23 pm Subject: How to repeat vectors ? To: r-help@stat.math.ethz.ch Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best -- Adrian DUSA Arhiva Romana de Date Sociale Bd. Schitu Magureanu nr.1 050025 Bucuresti sectorul 5 Romania Tel./Fax: +40 21 3126618 \ +40 21 3120210 / int.101 __ R-help@stat.math.ethz.ch 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] How to repeat vectors ?
Here are 4 approaches in order from most compact to least. #1 only works for numeric matrices, # 2 is a shorter versio of your solution using rep.vec and # 3 is from Alex's post and is likely what I would use in practice. m - matrix(1:4, 2) # test matrix # 1 - m must be numeric for this one to work kronecker(m, rep(1,2)) # 2 apply(m, 2, rep, each = 2) # 2 # 3 - from Alex's post m[rep(1:nrow(m), each = 2),] # 4 matrix(rbind(c(m), c(m)), nc = ncol(m)) On 9/30/06, Tong Wang [EMAIL PROTECTED] wrote: I just figured out a way to do this: rep.vec - function(X,n)return(t(array(rep(X,n),c(length(X),n Then,apply(MyMatrix, 2, rep.vec,2) Is there a better way ? Is there an internal function to repeat a vector or matrix ? Thanks a lot. - Original Message - From: Tong Wang [EMAIL PROTECTED] Date: Friday, September 29, 2006 11:23 pm Subject: How to repeat vectors ? To: r-help@stat.math.ethz.ch Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best __ R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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] How to repeat vectors ?
Here are some timings. From fastest to slowest we have: #3, #4, #1, #2 so, yes, the apply approach, even with the improvement (#2), is the slowest and, in fact, on this test is an order of magnitude slower than #3 which is the fastest one. m - matrix(1:4, 200) # test matrix # 1 - m must be numeric for this one to work system.time(for(i in 1:100)kronecker(m, rep(1,2))) [1] 2.93 0.29 3.34 NA NA # 2 system.time(for(i in 1:100)apply(m, 2, rep, each = 2)) [1] 5.22 0.09 5.73 NA NA # 3 - from Alex's post system.time(for(i in 1:100)m[rep(1:nrow(m), each = 2),]) [1] 0.50 0.07 0.60 NA NA # 4 system.time(for(i in 1:100)matrix(rbind(c(m), c(m)), nc = ncol(m))) [1] 1.54 0.20 1.77 NA NA On 10/1/06, Tong Wang [EMAIL PROTECTED] wrote: Hi, Thanks you guys for all the help. I learned a lot from it. It looks using apply() is not an efficient way, since all it does is looping through each row(or col) , which would be slow for large matrix, right ? cheers - Original Message - From: Gabor Grothendieck [EMAIL PROTECTED] Date: Saturday, September 30, 2006 4:54 am Subject: Re: [R] How to repeat vectors ? To: Tong Wang [EMAIL PROTECTED] Cc: r-help@stat.math.ethz.ch Here are 4 approaches in order from most compact to least. #1 only works for numeric matrices, # 2 is a shorter versio of your solution using rep.vec and # 3 is from Alex's post and is likely what I would use in practice. m - matrix(1:4, 2) # test matrix # 1 - m must be numeric for this one to work kronecker(m, rep(1,2)) # 2 apply(m, 2, rep, each = 2) # 2 # 3 - from Alex's post m[rep(1:nrow(m), each = 2),] # 4 matrix(rbind(c(m), c(m)), nc = ncol(m)) On 9/30/06, Tong Wang [EMAIL PROTECTED] wrote: I just figured out a way to do this: rep.vec - function(X,n) return(t(array(rep(X,n),c(length(X),n Then,apply(MyMatrix, 2, rep.vec,2) Is there a better way ? Is there an internal function to repeat a vector or matrix ? Thanks a lot. - Original Message - From: Tong Wang [EMAIL PROTECTED] Date: Friday, September 29, 2006 11:23 pm Subject: How to repeat vectors ? To: r-help@stat.math.ethz.ch Hi, If I have a matrix , say a11 a12 a21 a22 Is there a routine to get: a11 a12 a11 a12 a21 a22 a21 a22 Thanks a lot for any help. best __ R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
