Image file "fd_smooth01/directions.mif" does not contain fixel data (wrong dimensions)

I tried to run fixelcfestats commands from step 23 for performing statistical analysis:Fibre density and cross-section - Multi-tissue CSD — MRtrix 3.0 documentation, after running all the previous steps.
I get the following error:
[ERROR] Image file “fd_smooth01/directions.mif” does not contain fixel data (wrong dimensions)

[ERROR] Input data not successfully loaded: “directions.mif”

Hi @yichao,

The fact that your directory contains a file called “IN.mif” suggests that there has been some misunderstanding or mis-application of the for_each script; please see relevant documentation page and back-track through the linked documentation page to find where the error has first occurred.

The input text file containing the list of participant data, called files.txt here, should contain a list of file names for files containing subject data. Files “directions.mif” and “index.mif” form a part of the fixel directory format, and do not provide input quantitative fixel data for statistical analysis, so should be excluded from the contents of that text file.