How to add labels to PLOTMATRIX charts??



plotmatrix is a nice feature. But it seems to be hard to add labels
or legends. The only way I could add some sort of labels is by using
text(x, y, 'string') and replacing the plots on the diagonal with the
texts. But I want to keep the histograms on the diagonals.

Does anyone know a better way to add labels/legends to plotmatrix?
Thanks!
.