[R] Use of outer

[Rafael Jimenez]

On Sun, 12 Oct 2003, Spencer Graves wrote:

> I get
>
>  > var(as.vector(z.matrix))
> [1] 0
>
> I got sensible results from the following:
>
>  z.matrix <- outer(theta.1, theta.2, "+")
>  >
>  > ## Plot
>  > contour(theta.1, theta.2, z.matrix)
>
> hope this helps.  spencer graves

Thanks for the pointer.

A constant matrix is obtained with my call to 'outer'. However, the call
to outer seems to work fine when a function that takes two arguments
only is used. I guess the problem is in my definition of the function
'J', which depends on four arguments, but I couldn't figure out how to
make it work.

-Rafael

[...]
> >## ============================================= CODE
> >## Create vectors and matrix
> >Y <- c(0.5116403,2.4055245,1.6596707,1.8286057,2.6119199)
> >
> >col.1 <- c(0.8997692,0.8216292,0.6449104,0.8179743,0.6602276)
> >col.2 <- c(0.01175669,0.89389797,0.19913807,0.29872301,0.66144258)
> >
> >X <- cbind(col.1, col.2)
> >
> >## Define function
> >## Give default values so that it "takes two arguments"
> >J <- function (x1, x2, X.val=X, Y.val=Y) {
> >    t(Y.val-X.val[,1]*x1-X.val[,2]*x2) %*% (Y.val-X.val[,1]*x1-X.val[,2]*x2)
> >}
> >
> >## Get grid to plot
> >theta.1 <- array(seq(-1, 1, length=10))
> >theta.2 <- theta.1
> >
> >## How to do this with outer?
> >z.matrix <- outer(theta.1, theta.2, "J")
> >
> >## Plot
> >contour(theta.1, theta.2, z.matrix)
> >
> >______________________________________________
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> >
> >
>
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