# How to average FODs
**URL:** https://community.mrtrix.org/t/how-to-average-fods/4622
**Category:** Uncategorized
**Created:** [March 3, 2021, 4:11am UTC](https://community.mrtrix.org/t/how-to-average-fods/4622 "2021-03-03T04:11:21Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@mschira](https://community.mrtrix.org/u/mschira)
#### Post date: [March 3, 2021, 4:11am UTC](https://community.mrtrix.org/t/how-to-average-fods/4622/1 "2021-03-03T04:11:21Z")
Hi
I have several DWI scans from the same subject and I want to combine these on the FOD level.
I have successfully aligned all the scans using ANTs and I have applied the ANTs nonlinear transforms successfully to the FOD images.
> [@Registration: using transformations generated from other packages](https://community.mrtrix.org/t/registration-using-transformations-generated-from-other-packages/2259):
>
> The [mrtransform](https://mrtrix.readthedocs.io/en/latest/reference/commands/mrtransform.html) allows the spatial transformation of images when provided with a suitable linear or nonlinear transformation (“warp”). For linear transformations, MRtrix3 uses homogeneous transformation matrices stored as plain text. These can be converted from FSL and ITK-based (plain text) convention with the command [transformconvert](https://mrtrix.readthedocs.io/en/latest/reference/commands/transformconvert.html). The MRtrix3 tools expect nonlinear transformations in an image format where each voxel defines the scanner space location in the other image. This transformatio…
I have tested this, by estimating a DEC using fod2dec from the warped\_fod,mif and DEC aligns with the template.
So essentially, I now have several fod images in the exact same voxel space and I need to make an “average” (or combined) FOD.
What’s the right approach to do this? Can I just make an average?
Using mrcalc?
I can’t see a -average command? use -add and -divide?
M.
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### Author:  [@maxpietsch](https://community.mrtrix.org/u/maxpietsch)
#### Post date: [March 3, 2021, 8:29am UTC](https://community.mrtrix.org/t/how-to-average-fods/4622/2 "2021-03-03T08:29:30Z")
FODs can be averaged voxel-wise via the tool `mrmath`.
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### Author:  [@mschira](https://community.mrtrix.org/u/mschira)
#### Post date: [March 3, 2021, 12:50pm UTC](https://community.mrtrix.org/t/how-to-average-fods/4622/3 "2021-03-03T12:50:16Z")
Thanks,
voxelwise average, too easy.
Though I think mrcalc does that?
Anyway, can do.
M.
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### Author:  [@rsmith](https://community.mrtrix.org/u/rsmith)
#### Post date: [March 15, 2021, 4:49am UTC](https://community.mrtrix.org/t/how-to-average-fods/4622/4 "2021-03-15T04:49:05Z")
> voxelwise average, too easy.
> Though I think mrcalc does that?
While `mrcalc` _could_ do it, it would involve a whole lot of `... image1.mif -add image2.mif -add ...`.
`mrmath` not only doesn’t require you to keep specifying `-add` in between each pair, but also to use e.g. the wildcard character to grab many images with fewer keystrokes.