Hi Melissa,
Could it be that you added the age regressors in the .mat and .con files
later on in a text editor? That is, in both files the number of waves
and PPheights is set at 2, whereas you have specified 4 regressors. My
guess would be that this is causing the error in randomise. Best is to
remake the design files with the Glm GUI and then it will probably run
fine!
Cheers,
Ilya.
______________________________________
Ilya Veer
Leiden Institute for Brain and Cognition (LIBC)
Postzone C2-S
P.O. Box 9600
2300 RC Leiden
Tel. +31 71 526 1375
Visiting address:
LUMC
Dept. Radiology
K4 - room 44
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On
Behalf Of Steve Smith
Sent: Wednesday, November 12, 2008 10:28 AM
To: [log in to unmask]
Subject: Re: [FSL] randomise help
HI - I think this is similar to the query I answered a few days ago -
it is possible that the first two contrasts are illegal because
randomise can't generate permutations on a [1 0...] contrast when EV1
is all 1s (that's why we have the "-1" sign flipping option in
randomise).
But Matthew/Tom can confirm whether this is correct.
Cheers.
On 11 Nov 2008, at 21:13, Melissa Lopez-Larson wrote:
> Hello,
>
> I am attempting to compare 2 subject groups in vbm and I wanted to
> add age as another
> EV. I demeaned the data and set my design matrix and design
> contrast but get the error
> below. I have tried to change my matrix many times in the GLM and
> can not figure out
> what I am doing wrong.
> Thanks,
> Melissa
>
> /NumWaves 2
> /NumPoints 21
> /PPheights 1 1
> /Matrix
> 1 0 3.87 0
> 1 0 -0.63 0
> 1 0 3.26 0
> 1 0 2.75 0
> 1 0 -2.35 0
> 1 0 1.32 0
> 1 0 -1.41 0
> 1 0 0.79 0
> 1 0 -1.83 0
> 1 0 0.17 0
> 0.0 1.0 0 2.63
> 0.0 1.0 0 3.55
> 0.0 1.0 0 -3.76
> 0.0 1.0 0 -2.37
> 0.0 1.0 0 -0.59
> 0.0 1.0 0 -1.37
> 0.0 1.0 0 1.24
> 0.0 1.0 0 -1.99
> 0.0 1.0 0 -0.41
> 0.0 1.0 0 0.67
> 0.0 1.0 0 -1.83
>
>
>
> and my design.con as:
> /NumWaves 2
> /NumContrasts 4
> /PPheights 1 1
> /Matrix
> 1 0 0 0
> 0 1.0 0 0
> 1.0 -1.0 0 0
> -1.0 1.0 0 0
>
>
> However, I get the following error after the permutation have run:
>
> An exception has been thrown
> Runtime error:- detected by Newmat: matrix is singular
>
> MatrixType = Crout # Rows = 2; # Cols = 2
> Trace: Crout(lubksb); GeneralSolvI; InvertedMatrix::Evaluate.
>
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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