Detect abrupt changes in signal I'm using MATLAB and I'm trying to find the index of the first signal drop as shown in the figure bellow :


I tried the function findchangepts but it didn't give me the exact index, any solutions ?
A cheap and simple way is to differentiate the signal numerically and threshold the magnitude of differencate to identify the abrupt changes.While deciding the threshold you should take into account the dynamic range of the signal.