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Dear Kim,

That's right, T=Inf is the correct threshold.  I.e., there is
*no* threshold that will control FDR at 5%.

This might help:

load xSPM
Ps=xSPM.Ps;
S=xSPM.S;
P_FDR = spm_P_FDR(spm_invNcdf(1-Ps(1)),[1 Inf],'Z',1,Ps')
subplot(2,1,1)
plot((1:S)/S,Ps,'-o',(1:S)/S,(1:S)/S*P_FDR);xlim([0 0.5]);ylim([0 0.05])
title('Observed P versus Expected')
subplot(2,1,2)
loglog((1:S)/S,Ps,'-o',(1:S)/S,(1:S)/S*P_FDR);xlim([0 0.5]);ylim([0 0.05])
title('Observed P versus Expected, log-log')


As you'll see, P_FDR is 0.1789.  If you ask for FDR control at 0.2, you
should see some voxels.

-Tom


On Thu, Jul 21, 2011 at 12:38 PM, Guillaume Flandin <
[log in to unmask]> wrote:

> Dear Kim,
>
> I cannot see anything wrong, you seem to be in the situation where there
> is no signal in your data and the BH procedure, as implemented in SPM,
> returns Inf in this case.
>
> spm_uc_FDR(0.05,xSPM.df,xSPM.STAT,xSPM.n,xSPM.Ps')
>
> See slide 43 of this talk:
> http://www.fil.ion.ucl.ac.uk/spm/course/slides11/06_RFT_etc_FIL2011May.ppt
>
> You can also compute:
>  spm_invTcdf(1-0.05/33012,24) = 6.0479
> which is the 0.05 critical threshold, that your data do not reach.
>
> I copy this email to Tom Nichols who might be able to tell us more.
>
> Best regards,
> Guillaume.
>
>
> On 21/07/11 11:55, Veroude, K. wrote:
> > Dear Guillaume,
> >
> > Yes I changed topoFDR to 0 in SPM_defaults. Attached you can find the
> xSPM.mat.
> >
> > Thanks,
> >
> > Kim
> >
> > ________________________________________
> > Van: Guillaume Flandin [[log in to unmask]]
> > Verzonden: donderdag 21 juli 2011 12:12
> > Aan: Veroude, K.
> > Onderwerp: Re: [SPM] FDRp: Inf in SPM 8
> >
> > Dear Kim,
> >
> > so I assume that you are using voxel-wise FDR (ie you switched the
> > topoFDR option to false)?
> > When you are looking at this result, there should be a variable called
> > 'xSPM' in the MATLAB workspace, could you send it to me?
> >>> save xSPM.mat xSPM
> >
> > Many thanks,
> > Guillaume.
> >
> >
> > On 21/07/11 08:32, Veroude, K. wrote:
> >> Dear Guillaume,
> >>
> >> This is the Results window we get when applying FDR correction at p <
> 0.05. Any help would be appreciated.
> >>
> >> Best wishes,
> >>
> >> Kim
> >>
> >>
> >> -----Oorspronkelijk bericht-----
> >> Van: Guillaume Flandin [mailto:[log in to unmask]]
> >> Verzonden: woensdag 20 juli 2011 16:27
> >> Aan: Veroude, K.
> >> Onderwerp: Re: [SPM] FDRp: Inf in SPM 8
> >>
> >> Dear Kim,
> >>
> >> can you give me more details on what you are observing? A screenshot of
> >> the Results Graphics window would be useful to start with.
> >>
> >> Best regards,
> >> Guillaume.
> >>
> >>
> >> On 20/07/11 09:40, Kim Veroude wrote:
> >>> Hi,
> >>>
> >>> We have a similar problem, when applying FDR correction in SPM8 it
> >>> shows T = Inf. Have you found a solution for this?
> >>>
> >>> Thanks!
> >>>
> >>> Kim
> >>>
> >>>
> >>
> >>
> >
> >
> > --
> > Guillaume Flandin, PhD
> > Wellcome Trust Centre for Neuroimaging
> > University College London
> > 12 Queen Square
> > London WC1N 3BG
>
>
> --
> Guillaume Flandin, PhD
> Wellcome Trust Centre for Neuroimaging
> University College London
> 12 Queen Square
> London WC1N 3BG
>



-- 
__________________________________________________________
Thomas Nichols, PhD
Principal Research Fellow, Head of Neuroimaging Statistics
Department of Statistics & Warwick Manufacturing Group
University of Warwick, Coventry  CV4 7AL, United Kingdom

Web: http://go.warwick.ac.uk/tenichols
Email: [log in to unmask]
Phone, Stats: +44 24761 51086, WMG: +44 24761 50752
Fax:  +44 24 7652 4532

Now out!
*Handbook of fMRI Data Analysis*, by RA Poldrack, JA Mumford & TE Nichols
http://go.warwick.ac.uk/tenichols/publications/books





-- 
__________________________________________________________
Thomas Nichols, PhD
Principal Research Fellow, Head of Neuroimaging Statistics
Department of Statistics & Warwick Manufacturing Group
University of Warwick, Coventry  CV4 7AL, United Kingdom

Web: http://go.warwick.ac.uk/tenichols
Email: [log in to unmask]
Phone, Stats: +44 24761 51086, WMG: +44 24761 50752
Fax:  +44 24 7652 4532

Now out!
*Handbook of fMRI Data Analysis*, by RA Poldrack, JA Mumford & TE Nichols
http://go.warwick.ac.uk/tenichols/publications/books