++ 3dANOVA: AFNI version=AFNI_2011_12_21_1014 (Dec 16 2015) [64-bit] ++ Authored by: B. Douglas Ward This program performs single factor Analysis of Variance (ANOVA) on 3D datasets
3dANOVA
-levels r : r = number of factor levels
- -dset\ 1 filename : data set for factor level 1
- . . .. . .
- -dset 1 filename data set for factor level 1
- . . .. . .
- -dset r filename data set for factor level r
- . . .. . .
-dset r filename data set for factor level r
[-voxel num] : screen output for voxel # num
- [-diskspace\ ] : print out disk space required for
- program execution
- [-mask\ mset] : use sub-brick #0 of dataset ‘mset’
- to define which voxels to process
[-debug level] : request extra output
[-ftr prefix] : F-statistic for treatment effect
[-mean i prefix] : estimate of factor level i mean
[-diff i j prefix] : difference between factor levels
[-contr c1...cr prefix] : contrast in factor levels
Modified ANOVA computation options: (December, 2005)
** For details, see http://afni.nimh.nih.gov/sscc/gangc/ANOVA_Mod.html
[-assume_sph] assume sphericity (zero-sum contrasts, only)
This allows use of the old_method for computing contrasts which sum to zero (this includes diffs, for instance). Any contrast that does not sum to zero is invalid, and cannot be used with this option (such as ameans).
The following command generates one AFNI ‘bucket’ type dataset:
- [-bucket\ prefix] : create one AFNI ‘bucket’ dataset whose
- sub-bricks are obtained by concatenating the above output files; the output ‘bucket’ is written to file with prefix file name
Example is based on a study with one factor (independent variable) called ‘Pictures’, with 3 levels:
- Faces, (2) Houses, and (3) Donuts
The ANOVA is being conducted on the data of subjects Fred and Ethel:
- 3dANOVA -levels 3
-dset 1 fred_Faces+tlrc -dset 1 ethel_Faces+tlrc
-dset 2 fred_Houses+tlrc -dset 2 ethel_Houses+tlrc
-dset 3 fred_Donuts+tlrc -dset 3 ethel_Donuts+tlrc
-ftr Pictures -mean 1 Faces -mean 2 Houses -mean 3 Donuts -diff 1 2 FvsH -diff 2 3 HvsD -diff 1 3 FvsD -contr 1 1 -1 FHvsD -contr -1 1 1 FvsHD -contr 1 -1 1 FDvsH -bucket fred_n_ethel_ANOVA
This program accepts datasets that are modified on input according to the following schemes:
‘r1+orig[3..5]’ {sub-brick selector} ‘r1+orig<100..200>’ {sub-range selector} ‘r1+orig[3..5]<100..200>’ {both selectors} ‘3dcalc( -a r1+orig -b r2+orig -expr 0.5*(a+b) )’ {calculation}
Also see HowTo#5 - Group Analysis on the AFNI website: http://afni.nimh.nih.gov/pub/dist/HOWTO/howto/ht05_group/html/index.shtml
The default output format is to store the results as scaled short (16-bit) integers. This truncantion might cause significant errors. If you receive warnings that look like this:
+ WARNING: TvsF[0] scale to shorts misfit = 8.09% – ** Beware
then you can force the results to be saved in float format by defining the environment variable AFNI_FLOATIZE to be YES before running the program. For convenience, you can do this on the command line, as in
3dANOVA -DAFNI_FLOATIZE=YES ... other options ...
++ Compile date = Dec 16 2015