nipy_tsdiffana - Man Page

nipy_tsdiffana – Analyze, plot time series difference metrics


nipy_tsdiffana [-h] [--out-file OUT_FILE] [--write-results] [--out-path OUT_PATH] [--out-fname-label OUT_FNAME_LABEL] [--time-axis TIME_AXIS] [--slice-axis SLICE_AXIS] filename


Runs the time series difference algorithm over a 4D image volume, often an FMRI volume.

It works in one of three modes:

Write-Results Option, Generated Files

When doing the time point analysis, we will make a difference volume between each time point and the next time point in the series. If we have T volumes then there will be (T-1) difference volumes. Call the vector of difference volumes DV and the first difference volume DV[0]. So DV [0] results from subtraction of the second volume in the 4D input image from the first volume in the 4D input image. The element-wise squared values from DV[0] is DV2[0].

The following images will be generated. <ext> is the input filename extension (e.g. ‘.nii’):

  • dv2_max_<label><ext>” : 3D image volume, where each slice S is slice from all of DV2 [0] (slice S) through DV2[T-1] (slice S) that has the maximum summed squared values. This volume gives an idea of the worst (highest difference) slices across the whole time series.
  • dv2_mean_<label><ext>” : the mean of all DV2 volumes DV2[0] .. DV[T-1] across the volume (time) dimension. Higher voxel values in this volume mean that time-point to time point differences tended to be high in this voxel.

We also write the mean signal at each time point, and the mean squared difference between each slice in time, as variables to a ‘npz’ file named “tsdiff_<label>.npz

The filenames for the outputs are of the form <out-path>/<some_prefix><label><file-ext> where <out-path> is the path specified by the --out-path option, or the path of the input filename; <some_prefix> is one of the standard prefixes above, <label> is given by --out-label, or by the filename of the input image (with path and extension removed), and <file-ext> is ‘.png’ for graphics, or the extension of the input filename for volume images. For example, specifying only the input filename /some/path/fname.img will generate filenames of the form /some/path/tsdiff_fname.png, /some/path/dv2_max_fname.img etc.


Positional Arguments


4D image filename

Optional Arguments


Show a help message and exit

--out-file OUT_FILE

Graphics file to write to instead of leaving image on screen


Graphics file to write to instead of leaving image on screen If specified, write diagnostic images and analysis variables, plot to OUT_PATH. Mutually incompatible with OUT_FILE

--out-path OUT_PATH

Path for output image files (default from filename path)

--out-fname-label OUT_FNAME_LABEL

Mid part of output image / plot filenames

--time-axis TIME_AXIS

Image axis for time

--slice-axis SLICE_AXIS

See Also

nipy_3dto4d(1), nipy_4d_realign(1), nipy_4dto3d(1), nipy_diagnose(1)

Referenced By

nipy_3dto4d(1), nipy_4d_realign(1), nipy_4dto3d(1), nipy_diagnose(1).

February 2023