From help-request at octave dot org Fri Feb  4 12:03:40 2005
Subject: Re: differential and integral calculus
From: Michael Creel <michael dot creel at uab dot es>
To: help at octave dot org
Date: Fri, 04 Feb 2005 15:59:49 +0100

On Friday 04 February 2005 15:15, billkreamer at bellsouth dot net wrote:

> > f(x)=(x^2-3x)*sin x
> > f'(x)=?
>
> Athough Octave will not provide a symbolic answer for the above example,
> you can use the formula below to provide approximations for plotting the
> derivative:
>
> f'(x) = limit[as dx approaches zero]((f(x + dx) - f(x))/dx)
>
> Choose dx to whatever accuracy you desire.

You might also try numgradient, in octave-forge. In that function, dx is 
chosen automatically, with the aim of improving accuracy.
M.



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