Perfect!
Thank you very much!
Last question regarding these kinds of conversions:
How do I determine the corrected and the uncorrected p-value for a given
Z-value?
Thank you again!
All the best,
-Lucas
> Dear Lucas,
>
> No. ptoz is an FSL-command. Its syntax is (for a p=0.05)
>
> ptoz 0.05 -g <number of resels>
>
> Number of resels can be calculated based on the 'smoothest' command or
> (even better) based on the information you can find in the
> "*.feat/stats/smoothness" file:
>
> number of resels = VOLUME / RESELS
>
> Then, the 'ptoz' command will give you the z-threshold for p = 0.05
> (or any) corrected for FWE
> In the next step, you just have to threshold your zstat with the given
> z-value:
>
> After you have stored the VOLUME and RESEL information in the
> respective variable: e.g.:
>
> VOLUME=47487
> RESEL=2.34
>
> NRES=`echo "scale=4; $VOLUME / $RESEL" | bc`; # you need 'bc', because
> this is a floating point operation
> Z=`ptoz 0.05 -g $NRES`;
> fslmaths zstat1 -thr $Z $thresholded_zstat1
>
> I hope it helps,
>
> Auer, Tibor M.D. Ph.D.
> Biomedizinische NMR Forschungs GmbH
> am Max-Planck Institut für Biophysikalische Chemie
> Am Fassberg 11
> 37077 Göttingen
> Germany
> Phone/Work: +49-(0)551-201-1725
> Phone/Home: +49-(0)551-387-0076
> Mobile: +49-(0)176-8012-7921
> Mail: [log in to unmask]
>
>
>
> 2010.09.14. 13:36 keltezéssel, Lucas Eggert írta:
>> Dear Tibor,
>>> Dear Lucas,
>>>
>>> AFAIK, you cannot convert a z-map to FWE-p-map; but if your goal is
>>> to threshold your z-map with FWE, then you can calculate the
>>> z(p=0.05 FWE) threshold with ptoz command with using the -g switch.
>> That is exactly what I want to do: Determine the Z-value that
>> represents a p-value of e.g. 0.05 (FWE-corrected).
>>
>> However, I do not understand what you mean with '-g switch'. Do you
>> mean something like
>>
>> fslmaths zstat1.nii.gz -g -ptoz output.nii.gz?
>>
>> Thank you very much!
>> -Lucas
>>
>>>
>>> Bests,
>>>
>>> Auer, Tibor M.D. Ph.D.
>>> Biomedizinische NMR Forschungs GmbH
>>> am Max-Planck Institut für Biophysikalische Chemie
>>> Am Fassberg 11
>>> 37077 Göttingen
>>> Germany
>>> Phone/Work: +49-(0)551-201-1725
>>> Phone/Home: +49-(0)551-387-0076
>>> Mobile: +49-(0)176-8012-7921
>>> Mail: [log in to unmask]
>>>
>>>
>>>
>>> 2010.09.14. 12:32 keltezéssel, Lucas Eggert írta:
>>>> Dear Experts!
>>>>
>>>> How can I determine the FWE-corrected p-Value for a given Z-value?
>>>>
>>>> I tried
>>>>
>>>> fslmaths zstat1.nii.gz -cpval fwe-corrected.nii.gz
>>>>
>>>> ... but that results in an image with only values of 1 in every voxel.
>>>>
>>>> Best wishes,
>>>> -Lucas
>>>>
>>>
>>>
>>
>>
>
>
--
Lucas Eggert, M.Sc.
Institute of Cognitive Science
University of Osnabrueck
Albrechtstrasse 28
D-49076 Osnabrueck
Germany
Phone: +49-541-969-44-28
Website: http://www.cogsci.uni-osnabrueck.de/~leggert/
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