The function does return the change point indices -- you just didn't call it with a return value to save them...that plot looks like the function does a really nice job--I wasn't aware of it.
>> help findchangepts
findchangepts finds abrupt changes in a signal
IPOINT = findchangepts(X) returns the index in X that corresponds to the most significant change in mean.
...
So, write your above as
iPts=findchangepts(t,'MaxNumChanges',5);
instead.
PS.
't' is a peculiar variable name to choose for the waveform, that would more normally be associated with the time vector. Clearly it is your data here, and what you choose is your call, but would seem more appropriate to use something more representative of what your data content is.
