Re: Using Fourier and InverseFourier instead of Convolve

• To: mathgroup at smc.vnet.net
• Subject: [mg85939] Re: Using Fourier and InverseFourier instead of Convolve
• From: "Dana DeLouis" <dana.del at gmail.com>
• Date: Thu, 28 Feb 2008 02:50:04 -0500 (EST)

```Just to add.  You may want to adjust FourierParameters to "signal
processing"

list1 = {3, 1, 4, 2};
list2 = {1, 2, 3, 4};

Out1 = ListConvolve[list1, list2, {1, -1}, 0]

{3, 7, 15, 25, 20, 22, 8}

SetOptions[{Fourier, InverseFourier}, FourierParameters -> {1, -1}];

n = Length[list1] + Length[list2] - 1

7

{3, 1, 4, 2, 0, 0, 0}

{1, 2, 3, 4, 0, 0, 0}

Out2 = Round[InverseFourier[Chop[Fourier[v1]*Fourier[v2]]]]

{3, 7, 15, 25, 20, 22, 8}

Out1 == Out2

True

--
Dana DeLouis

"Solomon, Joshua" <J.A.Solomon at city.ac.uk> wrote in message
news:fpooi0\$1cg\$1 at smc.vnet.net...
> OK, I must admit that I do not understand everything ListConvolve does,
but
> I get the convolution I need when I do
> ListConvolve[list1, list2, {1, -1}, 0]
> In particular, the output has the appropriate length:
> Length[list1]+Length[list2]-1.
> Now, I would like to get the identical using Fourier and InverseFourier.
> Is this possible? What is the appropriate syntax?
> j
>
>

```

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