The boxerrorbars style is only relevant to 2D data plotting. It is a combination of the boxes and yerrorbars styles. It requires 3, 4, or 5 columns of data. An additional (4th, 5th or 6th) input column may be used to provide variable (per-datapoint) color information (see linecolor and rgbcolor variable). The error bar will be drawn in the same color as the border of the box.
3 columns:  x  y  ydelta
4 columns:  x  y  ydelta xdelta        # boxwidth != -2
4 columns:  x  y  ylow  yhigh          # boxwidth == -2
5 columns:  x  y  ylow  yhigh  xdelta

The boxwidth will come from the fourth column if the y errors are given as "ydelta" and the boxwidth was not previously set to -2.0 (set boxwidth -2.0) or from the fifth column if the y errors are in the form of "ylow yhigh". The special case boxwidth = -2.0 is for four-column data with y errors in the form "ylow yhigh". In this case the boxwidth will be calculated so that each box touches the adjacent boxes. The width will also be calculated in cases where three-column data are used.

The box height is determined from the y error in the same way as it is for the yerrorbars style — either from y-ydelta to y+ydelta or from ylow to yhigh, depending on how many data columns are provided.

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