Hi:
This is kind of kludgy, but if the matrix and parallel vector are both
numeric, you could try something like
A <- matrix(rnorm(12), nrow = 3)
v <- 1:3
f <- function(x) c(sum(x[-length(x)]^2), x[length(x)])
t(apply(cbind(A, v), 1, f))
v
[1,] 8.196513 1
[2,] 1.414914 2
[3,] 2.436660 3
>From your description, it may just be easier to cbind the vector to the
matrix and then write your function for a single vector input.
If each column of the (combined) matrix represents a different parameter of
some function, then you could write a function using the column names as
arguments and use the mdply() function in package plyr as
# library(plyr)
mdply(m, fun)
where each row of m provides a set of arguments to the function. The
sequence in which the columns of m appear should match the order in which
they appear in the function. Here's a toy example to illustrate:
u <- as.data.frame(matrix(rpois(9, 5), nrow = 3))
u
V1 V2 V3
1 9 6 7
2 11 3 4
3 5 11 6
names(u) <- c('x', 'y', 'z')
w <- cbind(u, v) # using v from above
f <- function(x, y, z, v) 2 * x + y + z - v
mdply(w, f)
x y z v V1
1 9 6 7 1 30
2 11 3 4 2 27
3 5 11 6 3 24
HTH,
Dennis
On Fri, Nov 12, 2010 at 5:46 AM, Claudia Beleites <cbelei...@units.it>wrote:
> Dear list,
>
> I'm stuck with looking for a function of the *apply family, which I suppose
> exists already – just I can't find it:
>
> What I'm looking for is somewhere between sweep and mapply that does a
> calculation vectorized over a matrix and a vector:
>
> It should work complementary to sweep: for each row of the matrix, a
> different value of the vector should be handed over.
> Close to mapply because I need to go through different variables in a
> parallel fashion (at the moment a matrix and a vector).
>
> Kind of a mapply that hands over array slices.
>
> Maybe it is easiest with an example. This loop does what I want, but
> > A <- matrix (rnorm (12), 3)
> > A
> [,1] [,2] [,3] [,4]
> [1,] 0.1286 0.2888 -0.4435 -0.90966
> [2,] -1.6000 -1.0884 1.3736 0.07754
> [3,] 0.4581 1.5413 0.6133 -0.12131
> > v <- 1 : 3
>
> > f <- function (x, y) { # some function depending on vector x and skalar y
> + c (sum (x^2), y)
> + }
>
> > result <- matrix (NA, nrow = nrow (A), ncol = 2)
> > for (r in 1 : nrow (A))
> + result [r,] <- f (A [r,], v [r])
> > result
> [,1] [,2]
> [1,] 1.124 1
> [2,] 5.637 2
> [3,] 2.976 3
>
> The matrix will easily be in the range of 1e4 - 1e5 rows x 1e2 - 1e3
> columns, so I do not want to split it into a list and combine it afterwards.
>
> The reason why I ask for a function is partly also because I want to
> overload the functionality for a specific class and I don't think it's a
> good idea to invent a name for something that probably already exists.
>
> If this function does not exist, any ideas how I should call it?
>
> Thanks a lot,
>
> Claudia
>
> --
> Claudia Beleites
> Dipartimento dei Materiali e delle Risorse Naturali
> Università degli Studi di Trieste
> Via Alfonso Valerio 6/a
> I-34127 Trieste
>
> phone: +39 0 40 5 58-37 68
> email: cbelei...@units.it
>
> ______________________________________________
> R-help@r-project.org mailing list
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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