3 Nov
2004
3 Nov
'04
5:48 a.m.
'n' as in d^n/dx^n .
Somewhat confusingly, 'N' is being used in the docstring as a synonym for 'order' and is the number of discrete points used to evaluate the numerical derivative. I'm going to fix that.
For example, when n=2, and order=3, one is computing the second central derivative using 3 points [x0-dx, x0, x0+dx].
Normally, one would expect "order" to be an indication of the accuracy of the derivative. So, order=p should mean d^n/dx^n (exact answer) - (what's computed) = O(dx^p) where dx is the mesh spacing. Clearly, with three points for the second derivative, the order is only two, so this is clearly not a mathematically correct use of the word "order"... -- Giovanni Samaey