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MathGroup Archive 2007

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Re: 2D Convolution

  • To: mathgroup at smc.vnet.net
  • Subject: [mg76389] Re: 2D Convolution
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Mon, 21 May 2007 05:59:16 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <f29389$m7p$1@smc.vnet.net><f29bko$pjn$1@smc.vnet.net> <f2emd1$2r6$1@smc.vnet.net> <f2h96m$13g$1@smc.vnet.net>

Mathieu G wrote:
> CKWong a =E9crit :
>> Errata:
>> g should be the kernel in the function
>>
>> Convolve[f_, g_, x_?NumberQ, y_?NumberQ] := NIntegrate[f[
>>     xPrime, yPrime] *g[x - xPrime,
>>   y - yPrime], {xPrime, -=A1=DB, =A1=DB}, {yPrime, -=A1=DB,=
>  =A1=DB}]
>> Sorry for the snafu.
>>
>>
> Thank you for your replies!!
> 
> I have a few questions still since I am neither a mathematician  or a
> mathematica expert:
> 
> Is it necessary to use the <?NumberQ> part since using the Convolve
> function for anything else would be non-sense? Does that bring any
> improvement in the Mathematica computation?

The following FAQ should answer your questions: "How do I write a 
function which evaluates only when the argument is a number?" Available at
http://support.wolfram.com/mathematica/kernel/features/evalwhennumber.html

Regards,
Jean-Marc

> Why does it make a difference that the kernel is the f or g function?
> 
> Best regards,
> MG
> 



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