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tickbox variable: $invphaseflag -- add phase of pi
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default: 0 (FALSE)

The "invph" tickbox (center-left) inverts phase
of complex color scales, but is also used to
invert the ends of some real-valued colscales.

For Fourier-analyzed data, when $invphaseflag is
1 ("invph" is ticked), Pi phase is effectively
added to the time course, that is, f(t) ->
f(t+Pi).

This is equivalent to multiplying phase by -1.
