Level crossings

Detect level crossing of signals.

Description

LC_FAST calculates how many times a given input signal crosses a set of levels.
It is much faster than traditional algorithms being designed to handle big datasets.

• MATLAB release: MATLAB 7.6 (R2008a)

[Martin Lechner]

This function has problems with consecutive equal values. They are also counted as crossings.

lc_fast([0;1;1;1;1;1;0],1)
ans = 4

I would expect for the example above: 1

[Jos (10584)]

Just curious what you mean by "This algorithm is generally faster than traditional ones". What are the traditonal ones?

I would suspect that an operation using something using DIFF and SIGN, as in (not-tested) "sum(diff(sign(Signal-OneLevel))) ~= 0)" is faster (as well as shorter)

[roberto madia]

 "Traditional" algorithms means algorithms based on sum(diff(sign(Signal-OneLevel))) ~= 0) method.
For large datasets this routine is at least 5 times faster.

In case of consecutive equal values this routines calculates all crossings even tough they are all equals.