adam_pgsql
2011-Jan-27 15:18 UTC
[R] how to divide each element of a matrix by a specific value per column
Hi, I'd like to divide each element of a matrix by a specific value per column. These specific values are stored in a list. For example:> x <- c(1,2,3,4,5) > y <- matrix(c(1:30), nrow = 6)Now I want to divide each element in y[,1] by x[1], y[,2] by x[2] etc. I have tried this> my_function <- function(data, ind) data/ind > apply(y, 2, my_function, x)[,1] [,2] [,3] [,4] [,5] [1,] 1 7.0 13.0 19.0 25.0 [2,] 1 4.0 7.0 10.0 13.0 [3,] 1 3.0 5.0 7.0 9.0 [4,] 1 2.5 4.0 5.5 7.0 [5,] 1 2.2 3.4 4.6 5.8 [6,] 6 12.0 18.0 24.0 30.0 Warning messages: 1: In data/ind : longer object length is not a multiple of shorter object length 2: In data/ind : longer object length is not a multiple of shorter object length 3: In data/ind : longer object length is not a multiple of shorter object length 4: In data/ind : longer object length is not a multiple of shorter object length 5: In data/ind : longer object length is not a multiple of shorter object length but as you can see it is applying them by row rather than column. Any ideas how to do this? Is there a variable within 'apply' that can be used to determine which column of y is being processed? thanks for any help adam> sessionInfo()R version 2.11.1 (2010-05-31) x86_64-apple-darwin9.8.0 locale: [1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods base
Dennis Murphy
2011-Jan-27 15:40 UTC
[R] how to divide each element of a matrix by a specific value per column
Here's one way:
y/outer(rep(1, nrow(y)), x)
[,1] [,2] [,3] [,4] [,5]
[1,] 1 3.5 4.333333 4.75 5.0
[2,] 2 4.0 4.666667 5.00 5.2
[3,] 3 4.5 5.000000 5.25 5.4
[4,] 4 5.0 5.333333 5.50 5.6
[5,] 5 5.5 5.666667 5.75 5.8
[6,] 6 6.0 6.000000 6.00 6.0
Run the outer command by itself to see what it does.
HTH,
Dennis
On Thu, Jan 27, 2011 at 7:18 AM, adam_pgsql
<adam_pgsql@witneyweb.org>wrote:
>
> Hi,
>
> I'd like to divide each element of a matrix by a specific value per
column.
> These specific values are stored in a list. For example:
>
> > x <- c(1,2,3,4,5)
> > y <- matrix(c(1:30), nrow = 6)
>
> Now I want to divide each element in y[,1] by x[1], y[,2] by x[2] etc. I
> have tried this
>
> > my_function <- function(data, ind) data/ind
> > apply(y, 2, my_function, x)
> [,1] [,2] [,3] [,4] [,5]
> [1,] 1 7.0 13.0 19.0 25.0
> [2,] 1 4.0 7.0 10.0 13.0
> [3,] 1 3.0 5.0 7.0 9.0
> [4,] 1 2.5 4.0 5.5 7.0
> [5,] 1 2.2 3.4 4.6 5.8
> [6,] 6 12.0 18.0 24.0 30.0
> Warning messages:
> 1: In data/ind :
> longer object length is not a multiple of shorter object length
> 2: In data/ind :
> longer object length is not a multiple of shorter object length
> 3: In data/ind :
> longer object length is not a multiple of shorter object length
> 4: In data/ind :
> longer object length is not a multiple of shorter object length
> 5: In data/ind :
> longer object length is not a multiple of shorter object length
>
> but as you can see it is applying them by row rather than column. Any ideas
> how to do this? Is there a variable within 'apply' that can be used
to
> determine which column of y is being processed?
>
> thanks for any help
>
> adam
>
> > sessionInfo()
> R version 2.11.1 (2010-05-31)
> x86_64-apple-darwin9.8.0
>
> locale:
> [1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
> ______________________________________________
> 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.
>
[[alternative HTML version deleted]]
Marc Schwartz
2011-Jan-27 15:44 UTC
[R] how to divide each element of a matrix by a specific value per column
On Jan 27, 2011, at 9:18 AM, adam_pgsql wrote:> > Hi, > > I'd like to divide each element of a matrix by a specific value per column. These specific values are stored in a list. For example: > >> x <- c(1,2,3,4,5) >> y <- matrix(c(1:30), nrow = 6) > > Now I want to divide each element in y[,1] by x[1], y[,2] by x[2] etc. I have tried this > >> my_function <- function(data, ind) data/ind >> apply(y, 2, my_function, x) > [,1] [,2] [,3] [,4] [,5] > [1,] 1 7.0 13.0 19.0 25.0 > [2,] 1 4.0 7.0 10.0 13.0 > [3,] 1 3.0 5.0 7.0 9.0 > [4,] 1 2.5 4.0 5.5 7.0 > [5,] 1 2.2 3.4 4.6 5.8 > [6,] 6 12.0 18.0 24.0 30.0 > Warning messages: > 1: In data/ind : > longer object length is not a multiple of shorter object length > 2: In data/ind : > longer object length is not a multiple of shorter object length > 3: In data/ind : > longer object length is not a multiple of shorter object length > 4: In data/ind : > longer object length is not a multiple of shorter object length > 5: In data/ind : > longer object length is not a multiple of shorter object length > > but as you can see it is applying them by row rather than column. Any ideas how to do this? Is there a variable within 'apply' that can be used to determine which column of y is being processed? > > thanks for any help > > adamHere is one approach:> t(t(y) / x)[,1] [,2] [,3] [,4] [,5] [1,] 1 3.5 4.333333 4.75 5.0 [2,] 2 4.0 4.666667 5.00 5.2 [3,] 3 4.5 5.000000 5.25 5.4 [4,] 4 5.0 5.333333 5.50 5.6 [5,] 5 5.5 5.666667 5.75 5.8 [6,] 6 6.0 6.000000 6.00 6.0 You essentially transpose the 'y' matrix so that the normal vector cycling of 'x' is applied properly, then transpose the result back to the original orientation. HTH, Marc Schwartz
Henrique Dallazuanna
2011-Jan-27 15:50 UTC
[R] how to divide each element of a matrix by a specific value per column
Try this: sweep(y, 2, x, "/") On Thu, Jan 27, 2011 at 1:18 PM, adam_pgsql <adam_pgsql@witneyweb.org>wrote:> > Hi, > > I'd like to divide each element of a matrix by a specific value per column. > These specific values are stored in a list. For example: > > > x <- c(1,2,3,4,5) > > y <- matrix(c(1:30), nrow = 6) > > Now I want to divide each element in y[,1] by x[1], y[,2] by x[2] etc. I > have tried this > > > my_function <- function(data, ind) data/ind > > apply(y, 2, my_function, x) > [,1] [,2] [,3] [,4] [,5] > [1,] 1 7.0 13.0 19.0 25.0 > [2,] 1 4.0 7.0 10.0 13.0 > [3,] 1 3.0 5.0 7.0 9.0 > [4,] 1 2.5 4.0 5.5 7.0 > [5,] 1 2.2 3.4 4.6 5.8 > [6,] 6 12.0 18.0 24.0 30.0 > Warning messages: > 1: In data/ind : > longer object length is not a multiple of shorter object length > 2: In data/ind : > longer object length is not a multiple of shorter object length > 3: In data/ind : > longer object length is not a multiple of shorter object length > 4: In data/ind : > longer object length is not a multiple of shorter object length > 5: In data/ind : > longer object length is not a multiple of shorter object length > > but as you can see it is applying them by row rather than column. Any ideas > how to do this? Is there a variable within 'apply' that can be used to > determine which column of y is being processed? > > thanks for any help > > adam > > > sessionInfo() > R version 2.11.1 (2010-05-31) > x86_64-apple-darwin9.8.0 > > locale: > [1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8 > > attached base packages: > [1] stats graphics grDevices utils datasets methods base > > ______________________________________________ > 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. >-- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O [[alternative HTML version deleted]]