`islocalmin`

Marks the local minima of a vector.

Category: Data Import and Analysis > Preprocessing Data

Syntax

TF = islocalmin(A)

true where an element is smaller than its neighbors.

[TF, P] = islocalmin(A)

Also returns the prominence of each valley.

TF = islocalmin(A, 'MinProminence', m)

Keeps only valleys whose prominence is at least m.

Description

A local minimum is a point strictly smaller than the neighbors on both sides. It is the mirror image of islocalmax: the prominence of a valley measures how deep it is below the highest ridge that separates it from a deeper valley.

Input arguments

A: Numeric vector or matrix (columns are analyzed).
'MinProminence': Minimum depth a valley must have below its surroundings.

Output arguments

TF: Logical array the size of A.
P: Prominence values, zero at points that are not valleys.

Example

Valleys of a series

x = [3 1 3 0 3];
tf = islocalmin(x)
find(tf)

Output

tf = 1×5 logical array

   0   1   0   1   0
ans = 1×2

     2     4

islocalmin