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## Algorithm for conv, filter

**From**: |
Steve C. Thompson |

**Subject**: |
Algorithm for conv, filter |

**Date**: |
Thu, 8 Dec 2005 07:01:31 -0800 |

**User-agent**: |
Mutt/1.5.9i |

Hi,
I've got $5 on: `conv (a, b)' is implemented as `ifft (af, bf)'
where AF and BF are the FFTs of A and B (roughly speaking).
Trying to prove this, I glanced at the octave source code for
`conv' and I see that it calls `filter'. (From what I
understand, `filter' and `conv' are essentially the same but
`conv' returns a complete convolution while `filter' truncates
the samples.) However, I can't figure out what `filter' does
since I can only find the .oct file on my computer---Linux
version 2.6.12-9-686 (gcc version 3.4.5 20050809 (prerelease)
(Ubuntu 3.4.4-6ubuntu8)); GNU Octave, version 2.1.71
(i486-pc-linux-gnu)---I'm not sure what filter is doing.
Does the algorithm in `filter' take the IFFT of two FFTs?
Thanks in advance.
Steve
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**Algorithm for conv, filter**,
*Steve C. Thompson* **<=**