I have a cumulative sum of monotonic values that is a function of time (I don't have the analytic function, just the points). For each point along the function, I would like to know the slope. The issue is that the rate of change is very slow and a little noisy point-to-point so calculating the slope between adjacent points would yield a lot of noise. Is there a function in Octave which gives the slope across multiple points? I was thinking that the function would take the change in slope between a point and another point x samples previous, where x changes based on deviation from the mean slope (taken across the points between the two end points). Or is there a better way to calculate slope in this situation? The function looks something like this:
http://en.wikipedia.org/wiki/File:Monotonicity_example1.png