I was worried about getting "a little noise in the result", so I ran a
quick test in Matlab and Julia, and got almost exactly the same error. This
is the Matlab code:
Ts=0.01;
t=-10:Ts:10;
s=sinc(t);
sc=Ts*conv(s,s);
sc=sc(1000:3000);
sum((sc-s).*(sc-s))
ans =
0.3695
So, at least for accuracy, julia's conv implementation seems to be no worse
than Matlab's.
On Tue, Mar 4, 2014 at 7:19 AM, Toivo Henningsson <toivo....@gmail.com>wrote:
> Yes, with sufficient padding, you can compute a linear convolution (of
> finite length vectors) exactly using a circular convolution. The FFT might
> introduce a little noise in the result, but that is all.
>
>
> On Tuesday, 4 March 2014 13:12:48 UTC+1, Oliver Lylloff wrote:
>>
>> Well ok,
>>
>> Maybe I misunderstood the whole thing then but since fft assumes periodic
>> input then I don't see how it can be a linear convolution. I guess
>> Base.conv2 probably uses zero-padding to reduce wrap-around but in theory
>> it would still be a circular convolution. I'll read up on it :)
>>
>> Best,
>> Oliver
>>
>> Den tirsdag den 4. marts 2014 13.07.20 UTC+1 skrev Andreas Noack Jensen:
>>>
>>> Both conv and conv2 are linear convolutions but the implementations use
>>> the fft. Maybe the documentation could be more clear on that.
>>>
>>>
>>> 2014-03-04 13:01 GMT+01:00 Oliver Lylloff <oliver...@gmail.com>:
>>>
>>>> Thanks Tim.
>>>>
>>>> Can't believe I missed that - been working with Images.jl all day. Nice
>>>> job by the way, very useful.
>>>>
>>>> Best,
>>>> Oliver
>>>>
>>>> Den tirsdag den 4. marts 2014 12.48.01 UTC+1 skrev Tim Holy:
>>>>
>>>>> Images.jl's imfilter might be what you want.
>>>>> --Tim
>>>>>
>>>>> On Tuesday, March 04, 2014 03:38:15 AM Oliver Lylloff wrote:
>>>>> > Hello all,
>>>>> >
>>>>> > Is anyone aware of a linear convolution implementation?
>>>>> > The Base.conv and Base.conv2 functions are implemented with fft
>>>>> which makes
>>>>> > them circular convolution functions (as far as I know).
>>>>> >
>>>>> > I'm looking for something alike Matlabs conv2 or SciPys
>>>>> signal.convolve2d.
>>>>> >
>>>>> > Should be straightforward to implement though.
>>>>> >
>>>>> > Best,
>>>>> > Oliver
>>>>>
>>>>
>>>
>>>
>>> --
>>> Med venlig hilsen
>>>
>>> Andreas Noack Jensen
>>>
>>
