There must be more... see ToDo, they are mostly there

1-	There are problems when plotting negative values with logaritm axis.
	A possible soluction is the one used: use only positives values.
	A horrible side effect is that a "baseline" is drawn near zero

	Would't it be better to just plot nothing, and let the 
		warning: implicit conversion from complex matrix to real matrix
	message warn the user? Is this message enought?

	The way gnuplot does this is not plotting the negative values, but this
	in cumbersome to do in the script file. One would just plot with the back
	ground color the negative values.

2-	This is not a bug, but a PLplot feature: there is no autoscale, as
	in gnuplot. This means that, after the first plot, after executing hold(),
	further plotting will be clipped to the viewport defined by the first plot.
	IT IS possible to redefine the viewport, but the previous plots will not 
	be redrawn to the new viewport. Also, one would have to erase the previous
	frame box and draw a new one.

4-	`ginput' lets the cross-hair drawn in the plot. Don't know how to avoid it.
	SOLVED? issue 'plflush' at the command line

5-	bottom_title and top_title can't be used.

6-	In line 97 of __plr2__.m, int the 2.0.9.95 octave distribution, there is
	a typo:
		diag_r = diag (rho);  # typo: in original sources was diag(r)
