fmri_downsample

Description

FMRI_DOWNSAMPLE Spatially downsamples vectorized fMRI data by integer factor. Retains every Nth voxel along each spatial dimension (x, y, z), reducing data size for computationally expensive operations. The output is a sub-sampled vectorized brain (fewer voxels x T). Inverse: fmri_upsample.

Usage

fmri2 = fmri_downsample(fmri)
fmri2 = fmri_downsample(fmri, factor)

Inputs

  • FMRI: Vectorized fMRI data (228453 x T).

  • FACTOR: Downsampling factor (integer). Every FACTOR-th voxel is kept in each dimension. Default: 2 (keeps 1/8 of voxels).

Outputs

  • FMRI2: Downsampled vectorized data. Number of rows depends on FACTOR: factor=2: ~28542 voxels, factor=3: ~8468, etc.

Examples

small = fmri_downsample(data);         % factor 2
small = fmri_downsample(data, 3);      % factor 3
orig  = fmri_upsample(small);          % restore full resolution

See Also

  • fmri_upsample