       Re: iterative convolution, discret convolution N times

• To: mathgroup at smc.vnet.net
• Subject: [mg102458] Re: [mg102424] iterative convolution, discret convolution N times
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sun, 9 Aug 2009 18:22:12 -0400 (EDT)
• Reply-to: hanlonr at cox.net

```fd[x_] := Piecewise[{{x + 1, 0 < x < 4}}]

n = 4;

For[i = 1; convn = fd[x], i <= n, i++,
convn = DiscreteConvolve[convn /. m -> x,
fd[x], x, m, Assumptions -> m > 0];
Print[FullSimplify[convn]]]

NestList[DiscreteConvolve[# /. m -> x,
fd[x], x, m] &,
fd[x], n] // Rest // FullSimplify

Bob Hanlon

---- Anna <petitmouton at gmail.com> wrote:

=============
HI, I'm trying to do N time convulution of a density funtion called
"fd" with itself . I tried to write an algorithm as shown
For[i = 1; convn = fd, i <= N, i++,
convn = DiscreteConvolve[convn, fd , x, m, Assumptions -> m > 0];
Print[convn]]

The initial function fd(x) has x as input variable. After the
convolution, the results convn(m) is in the function of m instead of
x. That's the reason why the algorithm I wrote doesn't work after the
first iteration since the DiscreteConvolve function couldn't find the
input in a function as x anymore.

I would like to ask a question is there a way to change the variable
of a function? for exemple: how can I replace a function y = x+1 by y=m
+1 ???? and is there another way to easily do a convolution N times of
the same function? Thank you very much.
Best regards,
Victoria

```

• Prev by Date: Re: a^k+b^k+c^k = d^k+e^k+f^k, for k = 2,4, with a constraint
• Next by Date: Re: video on Presentations by Williams and Park
• Previous by thread: Presentations Update
• Next by thread: Create jpg image files of mathematical equations