Finds the (lowest) point in the Buffer at which the input signal lies in-between the two values, and returns the index. The fractional part of the index is suitable for linearly interpolating between the buffer slot values.
For example, if the Buffer contains [3, 21, 25, 26] and the input has the value 22, then the output will be 1.25, because the value 22 is in-between the values stored in indices 1 and 2 and in fact is one-quarter of the way along the interval between them.
IndexInBetween is the complement of IndexL.
index of the buffer.
the input signal.