[Homer-users] Error using ==> svd

[David Boas]

Glad that worked.

A negative intensity is not physical. If your device is giving you 
negative numbers for the measured optical power it means that you have a 
non-zero offset that needs to be corrected. To correct for this non-zero 
offset, I suggest you measure the signal you get with no light hitting 
the detector. Then you need to subtract this offset from your measured 
signals to get the true signal. This offset is usually not a problem if 
you have large signals and small offsets. But if the signal becomes 
comparable to the offset, then you will get large errors in your 
estimated OD and hemoglobin changes.

David


On 7/20/14, 1:49 PM, nicolas niermann wrote:
> Thank you.
>
> I found some zeros in the d matrix and changed their value.
> Now it works.
> The negative values doesn't bother the analysis.
> Thanks for your efforts
>
> ------------------------------------------------------------------------
> *Von:* David Boas <dboas at nmr.mgh.harvard.edu>
> *An:* homer-users at nmr.mgh.harvard.edu
> *Gesendet:* 14:38 Freitag, 18.Juli 2014
> *Betreff:* Re: [Homer-users] Error using ==> svd
>
> odds are that those 3 data files have data files of 0 or negative 
> values in the d matrix
>
> I suggest that you modify the d matrix in those files so that you 
> replace the 0 or negative values with a very small positive number
>
>
>
>
>
> On 7/18/14, 3:57 AM, nicolas niermann wrote:
>> Good morning,
>>
>> I'm doing my PhD at the Sports University Cologne and use Homer2 for 
>> data analysis.
>>
>> I transformed all my files into .nirs-files (allways did it the same 
>> way) and processed them (by pressing the "run" button).
>> 19 files worked and I got the HRF- 3 files constantly show the 
>> following error signal:
>>
>>
>> ??? Error using ==> svd
>> Input to SVD must not contain NaN or Inf.
>>
>> Error in ==> enPCAFilter at 82
>> [V,St,foo] = svd(c);
>>
>> Error in ==> EasyNIRS_Process at 88
>> eval( fcall );
>>
>> Error in ==> EasyNIRS>runNIRSsignalProcess at 1022
>> [procResult procInput err] = EasyNIRS_Process(hmr);
>>
>> Error in ==> EasyNIRS>popupmenuNIRSsignalProcess_Callback at 1435
>> runNIRSsignalProcess(iGrp,iSubj,iRun,handles);
>>
>> Error in ==> gui_mainfcn at 96
>> feval(varargin{:});
>>
>> Error in ==> EasyNIRS at 43
>> gui_mainfcn(gui_State, varargin{:});
>>
>> Error in ==>
>> @(hObject,eventdata)EasyNIRS('popupmenuNIRSsignalProcess_Callback',hObject,eventdata,guidata(hObject))
>>
>> ??? Error while evaluating uicontrol Callback
>>
>>
>> I transformed them again, controlled all the data for NaN or Inf but 
>> just can't find the error.
>> Has someone an idea what the error could be or where to look for the 
>> error in the .nirs-file??
>>
>> Best regards
>> Nicolas Niermann
>>
>>
>>
>>
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>
> -- 
> ==============================================================
> fNIRS 2014 Conference in Montreal Oct 10-12, 2014
> The conference is preceded by a one day educational workshop.
> Abstract Deadline Extended to June 23, 2014
> seehttp://fnirs2014.org  <http://fnirs2014.org/>  for more details
> ==============================================================
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-- 
==============================================================
fNIRS 2014 Conference in Montreal Oct 10-12, 2014
The conference is preceded by a one day educational workshop.
Abstract Deadline Extended to June 23, 2014
see http://fnirs2014.org for more details
==============================================================

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