Calculates the mean of the most recent length values, but only paying attention to values input while the trigger is greater than zero. One application of this is to calculate a running mean of values coming from FFT analysis.
While trig<=0, the last-measured mean is held constant.
The length argument is set at initialisation, and cannot be modulated. The length is directly reflected in the amount of real-time memory taken by this UGen, so please think carefully before using large values of length. Values in the low single- or double-figures are expected.