title: How to add a x-axis line to a figure? (matlab)
body: <p>I want to add a x-axis line at 0 to a Matlab figure so that I can compare my data to see if it is positive or negative when saving the figures to a jpg.  What is the best way to do this?  I know you can use <code>line()</code> but it just seems cumbersome because you need to specify the x and the y ranges.  Is there an easier way? </p>