Count the number of times that a vector of values changes sign.

Syntax

N,I  = ZeroCrossings(V)

Argument

Name

Description

V

A vector of real values.

Outputs

Name

Description

N

The number of crossings.

I

The indices just prior to crossings.

Example

Find the number of zero crossings for the vector [0, -1, -1, 2, 0, 2, -1].

Syntax

N, I = ZeroCrossings([0, -1, -1, 2, 0, 2, -1])

Results

N = 3

I = 3  4  6

Comments

Crossings are not counted for first or last points of 0. A crossing is counted if the sequence contains a zero, even if there is no actual sign change.