Sorry for not being more specific. My goal is to select the range directly from the chart as opposed to the datapoints. I have written a module that detects the minimum in any range but I want the range to be determined by clicking on or dragging a rectangle on the actual chart. For instance, in the attached graph, I would want to figure out the minimum peak around 1400 wavenumbers by selecting the range around the peak. I have it set up so that a user can type in a range and it will calculate the minimum, but it would be cooler if they could just click on the chart.

Thanks!

Test.png