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Daniel Gerlanc

2006-Aug-03 14:10 UTC

[R] Vectorizing a "for" loop

Hello all,

Consider the following problem:

There are two vectors:

rows <- c(1, 2, 3, 4, 5)
columns <- c(10, 11, 12, 13, 14)

I want to create a matrix with dimensions length(rows) x length(columns):

res <- matrix(nrow = length(rows), ncol = length(columns))

If "i" and "j" are the row and column indexes respectively,
the values
of the cells are abs(rows[i] - columns[j]).  The resultant matrix
follows:

     [,1] [,2] [,3] [,4] [,5]
[1,]    9   10   11   12   13
[2,]    8    9    10   11   12
[3,]    7    8      9   10   11
[4,]    6    7      8     9   10
[5,]    5    6      7     8    9

This matrix may be generated by using a simple "for" loop:

for(i in 1:length(rows)){
  for(j in 1:length(columns)){
    res[i,j] <- abs(rows[i] - columns[j])
  }
}

Is there a quicker, vector-based approach for doing this or a function
included in the recommended packages that does this?

Thanks!

-- Dan Gerlanc
Williams College

Neuro LeSuperHéros

2006-Aug-03 14:22 UTC

head link

[R] Vectorizing a "for" loop

Hi,

Try this:

rows <- c(1, 2, 3, 4, 5)
columns <- c(10, 11, 12, 13, 14)
expanded <-expand.grid(rows,columns)
abslist <-abs(ex$Var1-ex$Var2)
res <- matrix(abslist,nrow = length(rows), ncol = length(columns))

Neurorox

>From: "Daniel Gerlanc" <dgerlanc at gmail.com>
>Reply-To: dgerlanc at gmail.com
>To: r-help at stat.math.ethz.ch
>Subject: [R] Vectorizing a "for" loop
>Date: Thu, 3 Aug 2006 10:10:46 -0400
>
>Hello all,
>
>Consider the following problem:
>
>There are two vectors:
>
>rows <- c(1, 2, 3, 4, 5)
>columns <- c(10, 11, 12, 13, 14)
>
>I want to create a matrix with dimensions length(rows) x length(columns):
>
>res <- matrix(nrow = length(rows), ncol = length(columns))
>
>If "i" and "j" are the row and column indexes
respectively, the values
>of the cells are abs(rows[i] - columns[j]).  The resultant matrix
>follows:
>
>      [,1] [,2] [,3] [,4] [,5]
>[1,]    9   10   11   12   13
>[2,]    8    9    10   11   12
>[3,]    7    8      9   10   11
>[4,]    6    7      8     9   10
>[5,]    5    6      7     8    9
>
>This matrix may be generated by using a simple "for" loop:
>
>for(i in 1:length(rows)){
>   for(j in 1:length(columns)){
>     res[i,j] <- abs(rows[i] - columns[j])
>   }
>}
>
>Is there a quicker, vector-based approach for doing this or a function
>included in the recommended packages that does this?
>
>Thanks!
>
>-- Dan Gerlanc
>Williams College
>
>______________________________________________
>R-help at 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.

Thomas Lumley

2006-Aug-03 14:22 UTC

head link

[R] Vectorizing a "for" loop

On Thu, 3 Aug 2006, Daniel Gerlanc wrote:
> Hello all,
>
> Consider the following problem:
>
> There are two vectors:
>
> rows <- c(1, 2, 3, 4, 5)
> columns <- c(10, 11, 12, 13, 14)
>
> I want to create a matrix with dimensions length(rows) x length(columns):
>
> res <- matrix(nrow = length(rows), ncol = length(columns))
>
> If "i" and "j" are the row and column indexes
respectively, the values
> of the cells are abs(rows[i] - columns[j]).  The resultant matrix
> follows:
>
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    9   10   11   12   13
> [2,]    8    9    10   11   12
> [3,]    7    8      9   10   11
> [4,]    6    7      8     9   10
> [5,]    5    6      7     8    9
>
> This matrix may be generated by using a simple "for" loop:
>
> for(i in 1:length(rows)){
>  for(j in 1:length(columns)){
>    res[i,j] <- abs(rows[i] - columns[j])
>  }
> }
>
> Is there a quicker, vector-based approach for doing this or a function
> included in the recommended packages that does this?
>
abs(outer(rows,columns,"-"))


 	-thomas

Marc Schwartz (via MN)

2006-Aug-03 14:23 UTC

head link

[R] Vectorizing a "for" loop

On Thu, 2006-08-03 at 10:10 -0400, Daniel Gerlanc wrote:> Hello all,
> 
> Consider the following problem:
> 
> There are two vectors:
> 
> rows <- c(1, 2, 3, 4, 5)
> columns <- c(10, 11, 12, 13, 14)
> 
> I want to create a matrix with dimensions length(rows) x length(columns):
> 
> res <- matrix(nrow = length(rows), ncol = length(columns))
> 
> If "i" and "j" are the row and column indexes
respectively, the values
> of the cells are abs(rows[i] - columns[j]).  The resultant matrix
> follows:
> 
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    9   10   11   12   13
> [2,]    8    9    10   11   12
> [3,]    7    8      9   10   11
> [4,]    6    7      8     9   10
> [5,]    5    6      7     8    9
> 
> This matrix may be generated by using a simple "for" loop:
> 
> for(i in 1:length(rows)){
>   for(j in 1:length(columns)){
>     res[i,j] <- abs(rows[i] - columns[j])
>   }
> }
> 
> Is there a quicker, vector-based approach for doing this or a function
> included in the recommended packages that does this?
> 
> Thanks!
See ?outer
> outer(rows, columns, function(x, y) abs(x - y))     [,1] [,2] [,3] [,4] [,5]
[1,]    9   10   11   12   13
[2,]    8    9   10   11   12
[3,]    7    8    9   10   11
[4,]    6    7    8    9   10
[5,]    5    6    7    8    9

HTH,

Marc Schwartz

Petr Pikal

2006-Aug-03 14:24 UTC

head link

[R] Vectorizing a "for" loop

Hi

outer(rows, columns, function(x,y) abs(x-y))
shall do it.

HTH
Petr


On 3 Aug 2006 at 10:10, Daniel Gerlanc wrote:

Date sent:      	Thu, 3 Aug 2006 10:10:46 -0400
From:           	"Daniel Gerlanc" <dgerlanc at gmail.com>
To:             	r-help at stat.math.ethz.ch
Subject:        	[R] Vectorizing a "for" loop
Send reply to:  	dgerlanc at gmail.com
	<mailto:r-help-request at stat.math.ethz.ch?subject=unsubscribe>
	<mailto:r-help-request at stat.math.ethz.ch?subject=subscribe>
> Hello all,
> 
> Consider the following problem:
> 
> There are two vectors:
> 
> rows <- c(1, 2, 3, 4, 5)
> columns <- c(10, 11, 12, 13, 14)
> 
> I want to create a matrix with dimensions length(rows) x
> length(columns):
> 
> res <- matrix(nrow = length(rows), ncol = length(columns))
> 
> If "i" and "j" are the row and column indexes
respectively, the values
> of the cells are abs(rows[i] - columns[j]).  The resultant matrix
> follows:
> 
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    9   10   11   12   13
> [2,]    8    9    10   11   12
> [3,]    7    8      9   10   11
> [4,]    6    7      8     9   10
> [5,]    5    6      7     8    9
> 
> This matrix may be generated by using a simple "for" loop:
> 
> for(i in 1:length(rows)){
>   for(j in 1:length(columns)){
>     res[i,j] <- abs(rows[i] - columns[j])
>   }
> }
> 
> Is there a quicker, vector-based approach for doing this or a function
> included in the recommended packages that does this?
> 
> Thanks!
> 
> -- Dan Gerlanc
> Williams College
> 
> ______________________________________________
> R-help at 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.
Petr Pikal
petr.pikal at precheza.cz

Neuro LeSuperHéros

2006-Aug-03 14:25 UTC

head link

[R] Vectorizing a "for" loop

Sorry,

I used ex instead of expanded (was working name).

rows <- c(1, 2, 3, 4, 5)
columns <- c(10, 11, 12, 13, 14)
expanded <-expand.grid(rows,columns)
abslist <-abs(expanded$Var1-expanded$Var2)
res <- matrix(abslist,nrow = length(rows), ncol = length(columns))

D?sol? encore

Neuro

>From: "Daniel Gerlanc" <dgerlanc at gmail.com>
>Reply-To: dgerlanc at gmail.com
>To: r-help at stat.math.ethz.ch
>Subject: [R] Vectorizing a "for" loop
>Date: Thu, 3 Aug 2006 10:10:46 -0400
>
>Hello all,
>
>Consider the following problem:
>
>There are two vectors:
>
>rows <- c(1, 2, 3, 4, 5)
>columns <- c(10, 11, 12, 13, 14)
>
>I want to create a matrix with dimensions length(rows) x length(columns):
>
>res <- matrix(nrow = length(rows), ncol = length(columns))
>
>If "i" and "j" are the row and column indexes
respectively, the values
>of the cells are abs(rows[i] - columns[j]).  The resultant matrix
>follows:
>
>      [,1] [,2] [,3] [,4] [,5]
>[1,]    9   10   11   12   13
>[2,]    8    9    10   11   12
>[3,]    7    8      9   10   11
>[4,]    6    7      8     9   10
>[5,]    5    6      7     8    9
>
>This matrix may be generated by using a simple "for" loop:
>
>for(i in 1:length(rows)){
>   for(j in 1:length(columns)){
>     res[i,j] <- abs(rows[i] - columns[j])
>   }
>}
>
>Is there a quicker, vector-based approach for doing this or a function
>included in the recommended packages that does this?
>
>Thanks!
>
>-- Dan Gerlanc
>Williams College
>
>______________________________________________
>R-help at 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.

Eik Vettorazzi

2006-Aug-03 14:28 UTC

head link

[R] Vectorizing a "for" loop

res<-outer(rows,columns,FUN=function(x,y) abs(x-y))

will help you.

Am Thu, 03 Aug 2006 16:10:46 +0200 schrieb Daniel Gerlanc  
<dgerlanc at gmail.com>:
> Hello all,
>
> Consider the following problem:
>
> There are two vectors:
>
> rows <- c(1, 2, 3, 4, 5)
> columns <- c(10, 11, 12, 13, 14)
>
> I want to create a matrix with dimensions length(rows) x length(columns):
>
> res <- matrix(nrow = length(rows), ncol = length(columns))
>
> If "i" and "j" are the row and column indexes
respectively, the values
> of the cells are abs(rows[i] - columns[j]).  The resultant matrix
> follows:
>
>      [,1] [,2] [,3] [,4] [,5]
> [1,]    9   10   11   12   13
> [2,]    8    9    10   11   12
> [3,]    7    8      9   10   11
> [4,]    6    7      8     9   10
> [5,]    5    6      7     8    9
>
> This matrix may be generated by using a simple "for" loop:
>
> for(i in 1:length(rows)){
>   for(j in 1:length(columns)){
>     res[i,j] <- abs(rows[i] - columns[j])
>   }
> }
>
> Is there a quicker, vector-based approach for doing this or a function
> included in the recommended packages that does this?
>
> Thanks!
>
> -- Dan Gerlanc
> Williams College
>
> ______________________________________________
> R-help at 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.
>


-- 
--------------------

Universit?t Hamburg
Institut f?r Statistik und ?konometrie
Dipl.-Wi.-Math. Eik Vettorazzi
Von-Melle-Park 5
20146 Hamburg

Tel.: +49 40-42838-3540

Dimitris Rizopoulos

2006-Aug-03 14:36 UTC

head link

[R] Vectorizing a "for" loop

try this:

abs(outer(rows, columns, "-"))


Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Daniel Gerlanc" <dgerlanc at gmail.com>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, August 03, 2006 4:10 PM
Subject: [R] Vectorizing a "for" loop

> Hello all,
>
> Consider the following problem:
>
> There are two vectors:
>
> rows <- c(1, 2, 3, 4, 5)
> columns <- c(10, 11, 12, 13, 14)
>
> I want to create a matrix with dimensions length(rows) x 
> length(columns):
>
> res <- matrix(nrow = length(rows), ncol = length(columns))
>
> If "i" and "j" are the row and column indexes
respectively, the
> values
> of the cells are abs(rows[i] - columns[j]).  The resultant matrix
> follows:
>
>     [,1] [,2] [,3] [,4] [,5]
> [1,]    9   10   11   12   13
> [2,]    8    9    10   11   12
> [3,]    7    8      9   10   11
> [4,]    6    7      8     9   10
> [5,]    5    6      7     8    9
>
> This matrix may be generated by using a simple "for" loop:
>
> for(i in 1:length(rows)){
>  for(j in 1:length(columns)){
>    res[i,j] <- abs(rows[i] - columns[j])
>  }
> }
>
> Is there a quicker, vector-based approach for doing this or a 
> function
> included in the recommended packages that does this?
>
> Thanks!
>
> -- Dan Gerlanc
> Williams College
>
> ______________________________________________
> R-help at 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.
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

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