TemporalSmoothingFD2D Method


Description

Filters in the frequency domain the time series of each voxel in the STC files of an FMR project. Can be used to remove linear and non-linear drifts (high-pass) and/or to smooth the time series (low-pass).

Syntax

objDocument.TemporalSmoothingFD2D(intHighPass, intLowPass)

Remarks

Valid only if objDocument is of type FMR. The high- and low pass values are interpreted in cycles per lenght of the time course measured in volumes. A high pass value of "3" removes frequency components below 3 cycles within the time series. A low pass value equal to or greater than half the length of the time series will have no effect (Nyquist theorem), i.e. the low-pass filter is turned off. If the time series data, for example, contains 256 measurements, then a low pass value of 128 or greater lets everything pass, i.e. it has no effect and is turned off. In the GUI version, BrainVoyager sets the default value of the low pass to one-third of the lenght of the time series which proved to produce good results, i..e. it results in slightly smoothed time series. It is, however, recommended, not to use low pass filtering at all when preprocessing data sets from event-related designs. This is also the reason, why low pass filtering is turned off in the GUI version (2D Data Preprocessing dialog) as default.
The resulting filtered data is automatically saved to disk. The names for the new FMR project and the new STC prefix is determined as in the GUI version, i.e., if the FMR project "cg_objects.fmr" is used, the resulting new file on disk will be "cg_objects_pp.fmr". In addition, a set of new STC files, actuallly containing the time series data, is stored to disk. If, for example, the prefix in the source FMR project was "slice-" (referencing file slice-1.stc, slice-2.stc etc.), the STC prefix of the new FMR file will be "slice_pp-". If you do not want to use this implicit naming scheme, you might want to use the method TemporalSmoothingFD2DEx which allows to specify the name of the resulting FMR project and STC prefix.

Example

' VBScript
Set doc = BrainVoyager.
OpenDocument("cg_objects.fmr")
doc.TemporalSmoothingFD2D 3, 200

// JScript
doc = BrainVoyager.
OpenDocument("cg_objects.fmr");
doc.TemporalSmoothingFD2D(3, 200);

# PerlScript
$doc = $BrainVoyager->
OpenDocument("cg_objects.fmr");
$doc->TemporalSmoothingFD2D(3, 200);