MATLAB: How to outline a curve

boundscurve fittingcurveshow to plotoutline

Hello.
If I'm trying to plot variables x and y, and the y values vary so much that the curve looks like the following: http://i.stack.imgur.com/4uiNT.png
The only difference is that mine is a single curve of data with a lot of noise. Is there a way I could just plot the upper and the lower curves so I could just look at the boundaries? Do I have to use the findpeak command?
Thank you for your time!