# Tck2Connectome on multiple tracks

**URL:** https://community.mrtrix.org/t/tck2connectome-on-multiple-tracks/772
**Category:** Uncategorized
**Tags:** connectomics
**Created:** [March 9, 2017, 1:30pm UTC](https://community.mrtrix.org/t/tck2connectome-on-multiple-tracks/772 "2017-03-09T13:30:31Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Alessandro](https://community.mrtrix.org/user_avatar/community.mrtrix.org/alessandro/32/2736_2.png) [@Alessandro](https://community.mrtrix.org/u/Alessandro)
#### Post date: [March 9, 2017, 1:30pm UTC](https://community.mrtrix.org/t/tck2connectome-on-multiple-tracks/772/1 "2017-03-09T13:30:31Z")

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Hi there,

I am trying to understand what happens when using tck2connectome to not-whole brain tracks.

Let us say I have TracksA.tck and TracksB.tck, and apply tck2connectome to obtain two matrices based on a given parcellation.

Is the sum of those two matrices equilavent to the output of tck2connectome applied to a tck file created by merging TracksA and TracksB tck files?

As secondary question, is there a way through mrtrix commands to merge multiple tck files?

Best Regards,

Alessandro

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### Author: ![rsmith](https://community.mrtrix.org/user_avatar/community.mrtrix.org/rsmith/32/2672_2.png) [@rsmith](https://community.mrtrix.org/u/rsmith)
#### Post date: [March 11, 2017, 7:39am UTC](https://community.mrtrix.org/t/tck2connectome-on-multiple-tracks/772/2 "2017-03-11T07:39:32Z")

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> Let us say I have TracksA.tck and TracksB.tck, and apply tck2connectome to obtain two matrices based on a given parcellation.

> Is the sum of those two matrices equilavent to the output of tck2connectome applied to a tck file created by merging TracksA and TracksB tck files?

_As long as_ the edge-wise statistic used when generating the connectome for each sub-tractogram is “`sum`” (which is the default), then yes, that is equivalent.

To explain the clarification: Imagine you are interested in the _minimum streamline length_ between each pair of nodes. So for each edge, `tck2connectome` internally tracks the minimum streamline length of all streamlines assigned to each edge, rather than “getting the streamline count”. If you were to do this for two separate track files, then taking the _sum_ of those two matrices is no longer the appropriate thing to do.

> As secondary question, is there a way through mrtrix commands to merge multiple tck files?

Yep: Simply provide multiple input images to `tckedit`.

Rob

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### Author: ![Alessandro](https://community.mrtrix.org/user_avatar/community.mrtrix.org/alessandro/32/2736_2.png) [@Alessandro](https://community.mrtrix.org/u/Alessandro)
#### Post date: [March 13, 2017, 8:44am UTC](https://community.mrtrix.org/t/tck2connectome-on-multiple-tracks/772/3 "2017-03-13T08:44:01Z")

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Hi @rsmith,  
thanks for your reply and additional comments!

Best,  
Alessandro