CONFPLOT is a linear plot utility, extending ERRORBAR to represent continuous confidence/error boundaries as a shaded gray area around the plotted line (i.e. taking advantage of the command 'area').
CONFPLOT(X,Y,L,U) plots the graph of vector X vs. vector Y with 'continuous' confidence/error boundaries specified by the vectors L and U. L and U contain the lower and upper error ranges for each point in Y. The vectors X,Y,L and U must all be the same length.