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. The clearance between the point and the error bars is
controlled by set pointintervalbox.
2 columns: [implicit x] y ydelta
3 columns: x y ydelta
4 columns: x y ylow yhigh
Additional input columns may be used to provide information such as variable
point size, point type, or color.
See also
http://www.gnuplot.info/demo/mgr.htmlerrorbar demo.
