Plotmatrix with variable names

Plotmatrix with variables names allowed

The help is not updated, but there is comments at the code. The function can be used with at least 4 inputs:

with 1
plotmatrix(x)

with 2
plotmatrix(x,y)
plotmatrix(x,linespec)
plotmatrix(x,varnames)

with 3
plotmatrix(x,linespec,varnames)
plotmatrix(x,y,linespec)
plotmatrix(x,y,varnames)

with 4
plotmatrix(x,y,varnames,linespec)

I'm using a lot the code and by now there isn't any problem