title: Python - Plotting vertical line
body: <p>I have a curve of some data that I am plotting using matplotlib.  The small value x-range of the data consists entirely of NaN values, so that my curve starts abruptly at some value of x>>0 (which is not necessarily the same value for different data sets I have).  I would like to place a vertical dashed line where the curve begins, extending from the curve, to the x axis.  Can anyone advise how I could do this? Thanks</p>