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Student Support Forum: 'Problem with computing convolutions' topicStudent Support Forum > General > Archives > "Problem with computing convolutions"

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Otje Fauzé
09/13/03 2:50pm

I have to compute the convolution of the functions |R -> |R

f: 0 if Abs[x]=>1
1 if Abs[x]<=1

g: 0 if x <= 0 or if x => 1
1 if 0 < x < 1

Trying something like:
Plot[NIntegrate[g[x - z], {z, -1, 1}], {x, -3, 3}]

works only after a lot of errors, while a simple Riemann-a-like integration like

\[Epsilon] = 1/1000
Plot[Sum[g[x - z] \[Epsilon], {z, -1, 1, \[Epsilon]}], {x, -3, 3}];

does work. I am using Mathematica 4.2. My questions:

1) Is there a way to compute such convolution symbolical (or by hand?). I can only guess how the convolution would look like, but I'd rather work out the integrals.
2) Why does NIntegrate give so much errors and takes such a long time?

Much thanks in advance,

Otje Fauzé

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Subject (listing for 'Problem with computing convolutions')
Author Date Posted
Problem with computing convolutions Otje Fauzé 09/13/03 2:50pm
Re: Problem with computing convolutions Henry Lamb 09/24/03 7:51pm
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