[PD] derivative function

Charles Henry czhenry at gmail.com
Tue Jun 27 00:10:55 CEST 2006


hmmm....simple way, use biquad~, you can put simple
integrators/differentiators in there

or make a more complicated differentiator using z~ objects and *~ and
+~ (or more than one biquad)

Your basic numerical differentiator is called a first forward difference:

f ' (n) = ( f(n+1) - f(n) ) / delta-T

next one, central divided difference

f ' (n) = ( f(n+1) - f(n-1) ) / 2delta-T
There are others......
and it all comes down to the truncation of a Taylor series anyway:

f(t) = f(0) + f'(0)*t + f''(0)/2! * t^2 + ...

and let's suppose we're approximating f'(0)

f'(0) = (f(t) - f(0) - f''(0)/2! * t^2 - ... ) / t

Those ...'s are where you need to supply numerical 3rd, 4th, 5th, and
such derivatives to improve the precision of your differentiator.
Numerical integration has more precise methods involved,
differentiation is always a numerical problem.

Doesn't have much to do with Fourier transforms or complex signals.
Chuck






On 6/26/06, Federico <xaero at inwind.it> wrote:
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> is there an object to compute the derivative function of a signal?
>
> don't know if derivative is the right term..
> i mean:
> f(x)=x      => f'(x)=1
> f(x)=ln(x)  => f'(x)=1/x
> f(x)=sin(x) => f'(x)=cos(x)
> ...
>
> and a more question: has this anything to do with complex signals or
> fourier?
>
> thanks
> - --
> Federico
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