Re: Derivation with Octave

[Ben Abbott]

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