I have written a small application using PyQt4 and matplotlib. Currently, I use the axes.add_line(Line2D Instance) to interact with the plot canvas. I am interested in allowing the user to add or remove error bars to the plot, but am unable to find a command to do so (e.g. set_yerr(self, numpy_array)). I am partial to the add_line() command as it allows me to create a Line2D instance with all of the relevant features (such as color, markersize etc.) and would like to avoid the pylab.errorbar() command. Does anyone have a solution to make error bars through matplotlib API?