# Visualizing t-statistics from age effects on tracts with mrview

**URL:** https://community.mrtrix.org/t/visualizing-t-statistics-from-age-effects-on-tracts-with-mrview/5071
**Category:** Uncategorized
**Tags:** tractography
**Created:** [July 23, 2021, 9:38am UTC](https://community.mrtrix.org/t/visualizing-t-statistics-from-age-effects-on-tracts-with-mrview/5071 "2021-07-23T09:38:19Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![josie](https://community.mrtrix.org/letter_avatar_proxy/v4/letter/j/f04885/32.png) [@josie](https://community.mrtrix.org/u/josie)
#### Post date: [July 23, 2021, 9:38am UTC](https://community.mrtrix.org/t/visualizing-t-statistics-from-age-effects-on-tracts-with-mrview/5071/1 "2021-07-23T09:38:20Z")

</div>

Hi MRtrixperts,

I am interested in typical developmental effects of fixel metrics:

> Some mean metric of different WM bundles ~ age + sex

For visualization purposes, I am trying to color the different WM bundle (tracts) based on the age t-value from my statistical model in mrview. I know it is possible to do so by loading a .txt file in the option of mrview in tractography. Does anyone have an example of such .tsf or .txt file? I have created a .txt file with the t-value, but it’s wrong because I always get:

> The scalar text file does not contain the same number of elements as the selected tractogram

How should one create this .txt file?

Thank you for all the help,  
Josiane

---

<div class="post-metadata">

### 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: [August 23, 2021, 7:22am UTC](https://community.mrtrix.org/t/visualizing-t-statistics-from-age-effects-on-tracts-with-mrview/5071/2 "2021-08-23T07:22:52Z")

</div>

Hi Josiane,

There’s a big difference between the operation of a `.tsf` vs. `.txt` file here. The former allows you to attribute some value _per streamline vertex_, whereas with the latter you can only attribute a value _per streamline_. If you have a statistical model parameter that is defined per fixel, the former simply involves sampling at each streamline vertex the value stored within the underlying fixel (currently via `fixel2tsf`). The latter would necessitate at least one extra operation.

What you’re most likely looking for (the former) is described in [this Wiki page](https://community.mrtrix.org/t/fba-post-statistical-inference-tricks/2255).

Rob

---

<div class="post-metadata">

### Author: ![josie](https://community.mrtrix.org/letter_avatar_proxy/v4/letter/j/f04885/32.png) [@josie](https://community.mrtrix.org/u/josie)
#### Post date: [September 2, 2021, 3:03pm UTC](https://community.mrtrix.org/t/visualizing-t-statistics-from-age-effects-on-tracts-with-mrview/5071/3 "2021-09-02T15:03:24Z")

</div>

Thanks Rob for the explanation !