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VoxelclassifyContent-type: text/html voxelclassifySection: User Commands (1)Index Return to Main Contents NAMEvoxelclassify - Classifies voxels according to the lowest-order spherical harmonic series needed to fit the data adequately.SYNOPSISvoxelclassify [-bgthresh <value>] [-csfthresh <maxA0>] [-order <maxOrder>] [-ftest <thresholds>]DESCRIPTIONComputes the spherical harmonic expansion of log(A(q)) in each voxel and uses an F-test to determine the simplest model that gives a good fit to the data.If F-test thresholds are specified, the program performs the F-Test and outputs the highest spherical harmonic order required to fit the data: 0 for isotropic data, 2 for anisotropic Gaussian, and 4 or more (up to the maximum) for anisotropic non-Gaussian data. Voxels classified as background (see OPTIONS) have order -1. If no f-test thresholds are specified on the command line, the program outputs all the f-statistics in each voxel for independent processing. These results are suitable for reading into the vcthreshselect program for interactive model selection. The format of the output for each voxel is:
OPTIONS
EXAMPLESClassify the data in image SubjectA.Bfloat, using no csf threshold. Classify all voxels with A(0) < 50.0 as background. The threshold for selecting an order 2 model is 1E-20, the thresholds for the order 4 and 6 model are 1E-6. voxelclassify -inputfile SubjectA.Bfloat -bgthresh 50.0 -schemefile A.scheme -order 6 -ftest 1E-20 1E-6 1E-6 > SubjectA.VC.Bint The next example does the same thing, but because no -ftest is specified, the program outputs the raw F-Test data for later analysis (eg with vcthreshselect(1)). voxelclassify -inputfile SubjectA.Bfloat -schemefile A.scheme -order 6 > SubjectA.VCthresholds.Bdouble AUTHORSDaniel Alexander <camino@cs.ucl.ac.uk>SEE ALSOvcthreshselect(1)BUGS
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