# [R] Plotting the correlation

Liaw, Andy andy_liaw at merck.com
Wed Apr 26 02:26:54 CEST 2006

```Try:

image.matrix <-
function (x, rlab = if (is.null(rownames(x))) 1:nrow(x) else
rownames(x),
clab = if (is.null(colnames(x))) 1:ncol(x) else colnames(x),
cex.row=0.7, cex.col=0.7, main = deparse(substitute(x)), ...)
{
op <- par(mgp=c(2, .3, 0))
on.exit(par(op))
nr <- nrow(x)
nc <- ncol(x)
image(1:nc, 1:nr, t(x)[, nr:1], axes = FALSE, xlab = "",
ylab = "", main = main, ...)
axis(2, 1:nr, rev(rlab), cex.axis=cex.col, tick=FALSE, las=2)
axis(1, 1:nc, clab, cex.axis=cex.row, tick=FALSE, las=2)
invisible(x)
}

image(yourMatrix)

Andy

From: Sasha Pustota
>
> Suppose I compute a correlation matrix ...
>
> r <- cor(log(rbind(iris3[,,1], iris3[,,2], iris3[,,3])))
>
> and then want to plot the values in color, e.g.
> image(r, col = terrain.colors(200))
>
> Why the matrix in the plot is rotated? The diagonal Rii=1
> goes from the bottom left to the upper right corner.
>
> Is there a way to plot the color values in the same
> orientation as the correlation matrix below? -
>
> > print.table(r, digits=2)
>          Sepal L. Sepal W. Petal L. Petal W.
> Sepal L.     1.00    -0.11     0.84     0.80
> Sepal W.    -0.11     1.00    -0.47    -0.45
> Petal L.     0.84    -0.47     1.00     0.97
> Petal W.     0.80    -0.45     0.97     1.00
>
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>

```