R help - Sep 2007 - Function modification: how to calculate values for every combination?

Hello,

I have a function like this:

fun <- function (x, y) {
          a <- log(10)*y
          b <- log(15)*x
          extr <- a-b
          extr
          }

fun(2,3)
[1] 1.491655

x <- c(1,2,3)
y <- c(4,5,6)
fun(x, y)
[1] 6.502290 6.096825 5.691360

How do I have to modify my function that I can calculate results using
every combination of x and y? I would like to produce a matrix which
includes the calculated values in every cell and names(x) and names(y)
as row and column headers respectively. Is the outer-function a way to
solution?

Best regards,
Lauri

On 9/2/07, Lauri Nikkinen <lauri.nikkinen at iki.fi>
wrote:
> I have a function like this:
>
> fun <- function (x, y) {
>           a <- log(10)*y
>           b <- log(15)*x
>           extr <- a-b
>           extr
>           }
>
> fun(2,3)
> [1] 1.491655
>
> x <- c(1,2,3)
> y <- c(4,5,6)
> fun(x, y)
> [1] 6.502290 6.096825 5.691360
>
> How do I have to modify my function that I can calculate results using
> every combination of x and y? I would like to produce a matrix which
> includes the calculated values in every cell and names(x) and names(y)
> as row and column headers respectively. Is the outer-function a way to
> solution?
Try the following code and adapt it to fill the matrix:

fun <- function (x, y) {
         a <- log(10)*y
         b <- log(15)*x
         extr <- a-b
         extr
}

x <- c(1,2,3)
y <- c(4,5,6)

combs <- expand.grid(x,y)

for (i in 1:nrow(combs))
  cat(fun(combs[i,1],combs[i,2]),"\n")

Paul

Yeah, exactly. Thanks. The solution was too obvious :-)

Cheers,
Lauri

2007/9/2, dtrenkle at uni-osnabrueck.de <dtrenkle at
uni-osnabrueck.de>:
> > Hello,
> >
> > I have a function like this:
> >
> > fun <- function (x, y) {
> >           a <- log(10)*y
> >           b <- log(15)*x
> >           extr <- a-b
> >           extr
> >           }
> >
> > fun(2,3)
> > [1] 1.491655
> >
> > x <- c(1,2,3)
> > y <- c(4,5,6)
> > fun(x, y)
> > [1] 6.502290 6.096825 5.691360
> >
> > How do I have to modify my function that I can calculate results using
> > every combination of x and y? I would like to produce a matrix which
> > includes the calculated values in every cell and names(x) and names(y)
> > as row and column headers respectively. Is the outer-function a way to
> > solution?
> >
> > Best regards,
> > Lauri
> >
> > ______________________________________________
> > 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.
> >
> >
>
> How about
>
> outer(x,y,fun)
>
> ?
>
> hth
>
> D. Trenkler
>
>

On 9/2/07, Paul Smith <phhs80 at gmail.com> wrote:
> > I have a function like this:
> >
> > fun <- function (x, y) {
> >           a <- log(10)*y
> >           b <- log(15)*x
> >           extr <- a-b
> >           extr
> >           }
> >
> > fun(2,3)
> > [1] 1.491655
> >
> > x <- c(1,2,3)
> > y <- c(4,5,6)
> > fun(x, y)
> > [1] 6.502290 6.096825 5.691360
> >
> > How do I have to modify my function that I can calculate results using
> > every combination of x and y? I would like to produce a matrix which
> > includes the calculated values in every cell and names(x) and names(y)
> > as row and column headers respectively. Is the outer-function a way to
> > solution?
>
> Try the following code and adapt it to fill the matrix:
>
> fun <- function (x, y) {
>          a <- log(10)*y
>          b <- log(15)*x
>          extr <- a-b
>          extr
> }
>
> x <- c(1,2,3)
> y <- c(4,5,6)
>
> combs <- expand.grid(x,y)
>
> for (i in 1:nrow(combs))
>   cat(fun(combs[i,1],combs[i,2]),"\n")
The complete code can be:

fun <- function (x, y) {
         a <- log(10)*y
         b <- log(15)*x
         extr <- a-b
         extr
}

x <- c(1,2,3)
y <- c(4,5,6)

combs <- expand.grid(x,y)

a <- vector()

for (i in 1:nrow(combs))
  a[i] <- fun(combs[i,1],combs[i,2])

m <- matrix(a,3,3)
rownames(m) <- x
colnames(m) <- y

m

Paul

outer(x,y,fun)

Lauri Nikkinen wrote:
> Hello,
> 
> I have a function like this:
> 
> fun <- function (x, y) {
>           a <- log(10)*y
>           b <- log(15)*x
>           extr <- a-b
>           extr
>           }
> 
> fun(2,3)
> [1] 1.491655
> 
> x <- c(1,2,3)
> y <- c(4,5,6)
> fun(x, y)
> [1] 6.502290 6.096825 5.691360
> 
> How do I have to modify my function that I can calculate results using
> every combination of x and y? I would like to produce a matrix which
> includes the calculated values in every cell and names(x) and names(y)
> as row and column headers respectively. Is the outer-function a way to
> solution?
> 
> Best regards,
> Lauri
> 
> ______________________________________________
> 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.
> 
> 

-- 
Erich Neuwirth, University of Vienna
Faculty of Computer Science
Computer Supported Didactics Working Group
Visit our SunSITE at http://sunsite.univie.ac.at
Phone: +43-1-4277-39464 Fax: +43-1-4277-39459

Just to add to this be sure you do have names if you want them
and read about vectorization in ?outer in case fun was just an
example and your actual fun is more complex:

x <- c(1,2,3)
names(x) <- x
y <- c(4,5,6)
names(y) <- y

outer(x, y, fun) # as in previous answer

# or
 outer(-log(15) * x, log(10) * y, "+")


On 9/2/07, Erich Neuwirth <erich.neuwirth at univie.ac.at>
wrote:
> outer(x,y,fun)
>
> Lauri Nikkinen wrote:
> > Hello,
> >
> > I have a function like this:
> >
> > fun <- function (x, y) {
> >           a <- log(10)*y
> >           b <- log(15)*x
> >           extr <- a-b
> >           extr
> >           }
> >
> > fun(2,3)
> > [1] 1.491655
> >
> > x <- c(1,2,3)
> > y <- c(4,5,6)
> > fun(x, y)
> > [1] 6.502290 6.096825 5.691360
> >
> > How do I have to modify my function that I can calculate results using
> > every combination of x and y? I would like to produce a matrix which
> > includes the calculated values in every cell and names(x) and names(y)
> > as row and column headers respectively. Is the outer-function a way to
> > solution?
> >
> > Best regards,