plegend:

Synopsis: Controls plot legend creationg for the current sub-plot.

Syntax: plegend ( DESCRIPTION )

Description:

	Plegend allows the user to enter a descriptive string(s) for
	the plot legend in the current sub-plot. DESCRIPTION can be a
	vector of strings, in which case the 1st string is used as the
	legend description for the 1st plotted column of data, the 2nd
	string is used as the description for the 2nd plotted column
	of data, and so-on. 

	If DESCRIPTION is "default", then the string(s) "cN" are used
	to denote from which column of the matrix the data belongs.

	If DESCRIPTION is undefined, then no legend is drawn. 
