How to find a minimum in a double peaked graph?

Hey all,

Please plot the data below. You can see that there is a graph with double peaks around 100 and 200. I want to find the minimum between these peaks. The problem is not only for this peak and I have a write a code which automatically finds the valley. How can I make a general code? In this graph I want the X=139 which is the min between two peaks. The mat file is uploaded here:

https://dl.dropboxusercontent.com/u/19202474/data.rar

Thanks in advance:) https://dl.dropboxusercontent.com/u/19202474/data.rar