Re: Derivation with Octave

[Julien Martin]

Hi there,
I tried Maxima and I find it awesome (just like Octave).
However, can any of you please explain to me the difference between numerical and symbolic calculus? 
When do I use Octave and when do I use Maxima?
Thanks in advance,
Julien.

2008/3/2, Ben Abbott <address@hidden>:

On Mar 2, 2008, at 8:32 AM, Julien Martin wrote:

> Hello,
> I am a beginner to Octave and would like to perform derivation on
> some functions. Can anyone please help? What is the syntax of the
> arguments of the differenciate function?
> Thanks in advance,
> Julien.


Octave a numerical (not a symbolic) computational tool. If you are
looking for symbolic derivatives, please consider Maxima.

For numerical derivatives, there are many methods to accomplish that
numerically.

Given you have a pair of vectors, x & y, where y is dependent upon x.

   dydx = diff (y) ./ diff (x);
   xc = x(1:end-1) + diff(x)/2;
   dydx = interp1 (x(n), dydx, xc, "linear", "extrap");

If the function, y, may be accurately represented by a polynomial of
order N

   dydx = polyval ( polyder ( polyfit (x, y, N)), x);


Ben