= Qdec Levels =
For each  discrete (categorical) factor, there could exist a file named <factor>.levels which lists all possible levels.  These are not necessary to run qdec, but can be used to control the order different factors are displayed. For example, accompanying the example {{{qdec.table.dat file}}}:

{{{
fsid  gender  age   Left-Hippocampus Right-Hippocampus
140   Female  18    4214             4190
049   Male    19    4543             4153
141   Female  20    3896             3741
084   Male    21    4804             4722
021   Male    22    4021             3969
093   Female  22    3603             3597
}}}

there could be an accompanying file named {{{gender.levels}}} containing these lines '''NOTE: make sure that the file ends with a new line''':

{{{
Female
Male
 
}}}

If many categorical factors are used, .levels files can be created for each one.  For example, if your qdec table also included a column called '''diagnosis''' with 3 levels (Control, AD, and MCI), a file called {{{diagnosis.levels}}} can be included, with these lines: 

{{{
Control
AD
MCI
 
}}}

The {{{<factor>.levels}}} files should be included in the same directory as the qdec table file.  Usual a {{{qdec}}} subdirectory is created inside the {{{SUBJECTS_DIR}}} to save these files, as well as the output of qdec analysis.