Propagation of Uncertainty

(UPDATE: Feel free to use this code, but I have written another much better code here: http://www.mathworks.com/matlabcentral/fileexchange/48139-worst-case-propagation-of-uncertainty)
Handy little function, for those of you in lab classes where they are sticklers for error. (or for those of you that are actual scientists even...!).

Propagation of uncertainty is a really slick formula, but its a massive pain to do by hand. this function does it for you!

To do it, just enter in the symbolic function, a row vector of the variables, a row vector for the estimated values of those variables, and lastly a row vector of the uncertainty associated with those variables.
help PropError has an example in it.
Enjoy!
outputs both actual error, and the percent error.

The program follows the equation shown in the screenshot. (courtesy of Wikipedia).
Requires Symbolic Math Toolbox.