outer
Generalized Outer Products
Description
Performs an outer product operation given two arrays (or vectors) and,
optionally, a function.
Usage
outer(X, Y, FUN = "*", ...)
X %o% Y #operator form
Arguments
| X, Y |
the first and second arguments to the function FUN.
Missing values (NAs) are allowed if FUN accepts them.
|
| FUN |
a function that takes at least two
vectors as arguments and returns a single value.
This may also be a character string giving the name of such a function.
|
| ... |
other arguments to FUN, if needed. The names of the arguments, if any,
must be meaningful to FUN.
|
Details
First, outer forms two arrays corresponding
to the data in X and Y,
each of which has a dim attribute formed by concatenating the
dim attributes of X and Y.
Second, outer calls FUN just once with these two arrays as arguments.
Therefore, FUN should be a function that operates element-wise
on vectors or arrays and expects (at least) two arguments.
The outer() function works best with input vectors that can be
contained in a matrix or an array. For example, you can use input vectors
with the class numeric or character, but input vectors of
a more complex class like timeDate or factor might not
produce useful results. In general, if you can use the replicate function,
rep(), to replicate the data values in the input vectors to any
arbitrary length, you can use the input vectors in an outer() calculation.
Value
returns an array whose dimension vector is the concatenation of the
dimension vectors of X and Y, such
that FUN(X[i,j,k,...], Y[a,b,c,...]) is the
value of the [i,j,k,...,a,b,c,...] element.
(Vectors are considered to be one-dimensional arrays.)
See Also
Examples
x <- runif(3)
y <- runif(4)
z <- x %o% y # The outer product array
# simulate a two-way table
outer(c(3.1, 4.5, 2.8, 5.2), c(2.7, 3.1, 2.8), "+") + matrix(rnorm(12),
nrow=4)
outer(month.name, 2010:2011, paste) # All month year combinations