:orphan: .. _ahelp_3dmatcalc: ********* 3dmatcalc ********* .. contents:: :local: | .. code-block:: none Usage: 3dmatcalc [options] Apply a matrix to a dataset, voxel-by-voxel, to produce a new dataset. * If the input dataset has 'N' sub-bricks, and the input matrix is 'MxN', then the output dataset will have 'M' sub-bricks; the results in each voxel will be the result of extracting the N values from the input at that voxel, multiplying the resulting N-vector by the matrix, and output the resulting M-vector. * If the input matrix has 'N+1' columns, then it will be applied to an (N+1)-vector whose first N elements are from the dataset and the last value is 1. This convention allows the addition of a constant vector (the last row of the matrix) to each voxel. * The output dataset is always stored in float format. * Useful applications are left to your imagination. The example below is pretty fracking hopeless. Something more useful might be to project a 3D+time dataset onto some subspace, then run 3dpc on the results. OPTIONS: ------- -input ddd = read in dataset 'ddd' [required option] -matrix eee = specify matrix, which can be done as a .1D file or as an expression in the syntax of 1dmatcalc [required option] -prefix ppp = write to dataset with prefix 'ppp' -mask mmm = only apply to voxels in the mask; other voxels will be set to all zeroes EXAMPLE: ------- Assume dataset 'v+orig' has 50 sub-bricks: 3dmatcalc -input v+orig -matrix '&read(1D:50@1,\,50@0.02) &transp' -prefix w The -matrix option computes a 2x50 matrix, whose first row is all 1's and whose second row is all 0.02's. Thus, the output dataset w+orig has 2 sub-bricks, the first of which is the voxel-wise sum of all 50 inputs, and the second is the voxel-wise average (since 0.02=1/50). -- Zhark, Emperor -- April 2006 ++ Compile date = Jun 14 2021 {AFNI_21.1.12:linux_ubuntu_16_64}