Draws y error bars at a set of points. This is usually used
before (under) a set of Dots at the same points.
YErrorBars(d, attribute=value)
d required list of (x,y,yerr...) points
attribute=value pairs keyword list SVG attributes
If points in d have
* 3 elements, the third is the symmetric error bar
* 4 elements, the third and fourth are the asymmetric lower and
upper error bar. The third element should be negative,
e.g. (5, 5, -1, 2) is a bar from 4 to 7.
* more than 4, a tick mark is placed at each value. This lets
you nest errors from different sources, correlated and
uncorrelated, statistical and systematic, etc.
Definition at line 3327 of file svgfig.py.