Thanks Chris. This is what I have done.

I guess I have to threshold the matrix somehow, although there is also much evidence published without thresholding. Do you have any suggestion for the threshold? According to a nice paper (Cao et al 2013, JNS), a threshold range between 0.01 and 0.1 at intervals of 0.0025 is may appropriate? How can I do this in matlab?

Many thanks again.

André

Von: FSL - FMRIB's Software Library [[log in to unmask]]" im Auftrag von "Watson, Christopher [[log in to unmask]]
Gesendet: Dienstag, 25. August 2015 17:20
An: [log in to unmask]
Betreff: Re: [FSL] fdt_network_matrix - no symmetry?

I don' think the order matters much, but dividing by waytotal first will save you a step or 2.

From: FSL - FMRIB's Software Library <[log in to unmask]> on behalf of André Schmidt <[log in to unmask]>
Sent: Tuesday, August 25, 2015 8:24 AM
To: [log in to unmask]
Subject: [FSL] AW: [FSL] fdt_network_matrix - no symmetry?

Hi Moises,

I guess I have figured out how to calculate the transpose matrix and the average of the two matrices.

Just a quick follow up question: I also like to normalize the matrix with the waytotal values. Should I do this before these calculations?

Also thanks for checking the recently sent seed mask, your help is highly appreciated.

Best wishes

André

Von: FSL - FMRIB's Software Library [[log in to unmask]]" im Auftrag von "Moises Hernandez [[log in to unmask]]
Gesendet: Dienstag, 25. August 2015 13:10
An: [log in to unmask]
Betreff: Re: [FSL] fdt_network_matrix - no symmetry?

Hi André,

They are not symmetric because you are running different experiments from each seeds-ROI.

First from left_thalamus to the rest.

Then from left_caudate to the rest.

etc...

So, you will get different results for left_thalamus->left_caudate (experiment 1)

and left_caudate->left_thalamus (experiment 2).

What you can do is to calculate the transpose of the Matrix and then average both Matrices.

Moises.

On 24 August 2015 at 16:57, André Schmidt <[log in to unmask]> wrote:

Dear fsl experts,

I have performed probtrackx2 on my DTI data and now like to compare the obtained fdt_network_matrix across two groups using network-based statistics. To do this, the connectivity matrices must be symmetric about the diagonal. However, I realized that this is not the case for the fdt network matrices (see attached an example for the matrix file and seed file). Why is the number of streamlines from region i to j not the same as from j to i? Can I symmetrize the matrix somehow?

Thank you very much for your explanations and help

Best wishes

André