Re: Using Fourier and InverseFourier instead of Convolve

• To: mathgroup at smc.vnet.net
• Subject: [mg85958] Re: Using Fourier and InverseFourier instead of Convolve
• From: "Solomon, Joshua" <J.A.Solomon at city.ac.uk>
• Date: Thu, 28 Feb 2008 02:59:56 -0500 (EST)
• References: <fpooi0\$1cg\$1@smc.vnet.net> <fq0u59\$k8l\$1@smc.vnet.net>

```First, let me thank all who responded to my query!
Second, no, Daniel, your code works fine for me.
Finally, FWIW here is code that does what I really wanted, which was to
quickly convolve a long list of lists (each having the same length).
Possibly not the most elegant code ever, but it works, as I said, FWIW:

cv[listOfLists_]:=With[{dims=Dimensions[listOfLists]},
(dims[[1]]dims[[2]]-dims[[1]]+1)^((dims[[1]]-1)/2)
InverseFourier[Times[##]]&@@(
]&/@listOfLists)]

On 26/2/08 11:45, in article fq0u59\$k8l\$1 at smc.vnet.net, "dh" <dh at metrohm.ch>
wrote:

> d1 = Table[If[Abs[i] < 3, 1, 0], {i, -5, 5}];
>
> ListLinePlot[{InverseFourier[Fourier[d1] Fourier[d1 ]] Sqrt[10] ,d1}]
>
> ListLinePlot[{ListConvolve[d1, d1, 1], d1}]
>
> ListLinePlot[{ListConvolve[d1, d1, -1], d1}]
>
> Note that the innocent code above crashes my mathematica kernel (version
>
> 6.1, does this happen to you too? )

```

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