The yerrorbars (or errorbars) style is only relevant to 2D data plots. yerrorbars is like points, except that a vertical error bar is also drawn. At each point (x,y), a line is drawn from (x,y-ydelta) to (x,y+ydelta) or from (x,ylow) to (x,yhigh), depending on how many data columns are provided. The appearance of the tic mark at the ends of the bar is controlled by set errorbars.
2 columns:  [implicit x] y ydelta
3 columns:  x  y  ydelta
4 columns:  x  y  ylow  yhigh

An additional input column (4th or 5th) may be used to provide information such as variable point color.

See also errorbar demo.

Copyright 1986 - 1993, 1998, 2004 Thomas Williams, Colin Kelley
Distributed under the gnuplot license (rights to distribute modified versions are withheld).