Slow Wave Upswing

Introduced in version 0.7.5, SWU is a poor man's take on measuring the local synchronicity of neurons acting together to produce a slow wave.

It is computed as a total sum, over a page, of area under the curve of the signal's first derivative where it is positive, discarding periods shorter than a certain threshold.

SWU should to be lower where slow waves have front interrupted by a ‘kink’. It may be extended to also degrade in presence of a slow wave terminating in a peak with many (rather than few) local minima.