Hi,

Thank you for the suggestions, I will try it via the fft.
Regarding the noise it is hard to assess how it looks like. To be more 
specific about what I want to do: I acquired fMRI data and trial 
averaged all the data, resulting in a single response profile for a 
specific event. This profile could be assumed to be the convolution of a 
neuronal response with a hemodynamic response function represented by a 
gamma kernel. However, the underlying neuronal activity is not just the 
response to a distinct event, but would be more complex, thus my idea to 
obtain the response by a deconvolution. With the extensive trial 
averaging I am hoping to cope with the severe noise, so that the 
averaged time course might represent more closely the result of the 
convolution. However, I might be wrong, and another problem would be, 
that I do not know anything about the baseline and thus have to 
determine one based on some assumptions. Therefore I am not entirely 
sure whether my approach makes any sense or is just waste of time. But 
if I could obtain reasonable results this would just be great.

Thanks again for your suggestions,
wolf
Moshe Olshansky wrote:
> Hi Wolf,
>
> Without noise you could use FFT, i.e. FFT of a convolution is the product of the individual FFTs and so you get the FFT of your input signal and using inverse FFT you get the signal itself. 
> When there is noise you must experiment. You may want to filter the response before doing FFT. Whay do you know about the noise?
>
> Regards,
>
> Moshe.
>
>
> --- On Mon, 25/8/08, wolf zinke <wolfzinke@gmx.net> wrote:
>
>   
>> From: wolf zinke <wolfzinke@gmx.net>
>> Subject: [R] deconvolution: Using the output and a IRF to get the input
>> To: r-help@r-project.org
>> Received: Monday, 25 August, 2008, 8:22 AM
>> Hi,
>>
>> Maybe someone could give me some pointers for my problem.
>> So far I have 
>> not found a good solution, maybe it is just ill posed?
>>
>> I have a signal that is the result of an input signal
>> convolved with a 
>> given impulse response function (IRF) plus noise. I want to
>> use the this 
>> signal and the IRF to determine the underlying input
>> signal. In my 
>> naivety I thought this just might be a deconvolution
>> problem. But here I 
>> found only routines that use the input signal and the
>> output signal to 
>> get the IRF. Is it possible to derive the input signal when
>> output and 
>> IRF are given? If so, how could I do this with R?
>>
>> Thanks a lot for any hints,
>> wolf
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
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>> and provide commented, minimal, self-contained,
>> reproducible code.
>>     
>
>   


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