[WIP] Preprocessing channel filtering

NIRS measurement are heterogeneous (long distance measurements, movements, occlusion by hair) and the signal in several channels might not be properly analysed. A first pre-processing step hence consists in removing those channels.

The following criterions may be applied to reject channels:

• some values are negative
• signal is flat (variance close to 0)
• signal has too many saturating points (equal to max or min)
• signal has too many null segments
• Scalp coupling index thresholding
• Channel distance thresholding

Process "NIRS -> Detect bad channels".

[TODO: snapshot of process panel]

• Remove negative channels: tag a channel as bad if it has a least one negative value. This is important for the quantification of delta [Hb] which cannot be applied if there are negative values. ''' '''
• Maximum proportion of saturating point: a saturating point has a value equals to the maximum of the signal. The default is at 1: remove only flat signals. If one wants to also keep flat channels, set the value to at least 1.01. ''' '''

This process is performed "in place": the channel flags of the given data are modified. To view the result, right-click on the NIRS data then "Good/Bad Channels > View all bad channels" or "Edit good/bad channels".