3) *.grid  ASCII-text file (output in ALL modes).
     Simple text file of output stats of WM-ROIs. It outputs the means and
     standard deviations of parameter quantities (such as FA, MD, L1, etc.)
     as well as counts of tracks and volumes of WM-ROIs. Each matrix is
     square, with dimension N_ROI by N_ROI. Like the locations in a standard
     correlation matrix, each element reflects associativity with target
     ROIs.  A value at element (1,3) is the same as that at (3,1) and tells
     about the property of a WM-ROI connecting target ROIs 1 and 3 (consider
     upper left corner as (1,1)); diagonal elements provide info of tracks
     through (at minimum) that single target ROI-- like OR logic connection.
     Format of *.grid file is:
     Line 1:  number of ROIs in network (padded with #-signs)
     Line 2:  number of output matrices of stats info (padded with #-signs)
     Line 3:  list of N_ROI labels for that network
     Lines following: first line, label of a property (padded with #), and 
                      then N_ROI lines of the N_ROI-by-N_ROI matrix of that
                      property;
                      /repeat/
     The first *five* matrices are currently (this may change over time):
         NT = number of tracks in that WM-ROI
         fNT = fractional number of tracks in that WM-ROI, defined as NT
               divided by total number of tracts found (may not be relevant)
         PV = physical volume of tracks, in mm^3
         fNV = fractional volume of tracks compared to masked (internally or
               '-mask'edly) total volume; would perhaps be useful if said
               mask represents the whole brain volume well.
         NV = number of voxels in that WM-ROI.
     Then, there can be a great variety in the remaining matrices, depending
     on whether one is in DTI or HARDI mode and how many scalar parameter
     files get input (max is 10). For each scalar file there are two
     matrices: first a label (e.g., 'FA') and then an N_ROI-by-N_ROI matrix
     of the means of that parameter in each WM-ROI; then a label (here,
     would be 'sFA') and then an N_ROI-by-N_ROI matrix of the standard
     deviations of that parameter in each WM-ROI.

Quote
L1 - direction 1