Find slope of function given empirical data.

[duncan smith]

Thomas wrote:
> Hello all.
> 
> Trying to find slope of function using numpy.
> Getting close, but results are a bit off. Hope someone out here can
> help.
> 

[snip]

Why are you generating y-coordinates from the x-coordinates [-6, -5, -4, 
-3, -2, -1, 0, 1, 2, 3, 4]?  If you're going to use the x-coordinates 
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0] in your function, then use the same 
to generate the y-coordinates.  Surely, if you have empirical data 
(which, for some reason, you know are well fitted by a quadratic 
function?) you'd pass both the x and y coordinates to the function? 
Maybe (untested),

def deriv(x, y):
     z = np.polyfit(x, y, 2)
     p = np.poly1d(z)
     return p.deriv()

Duncan