Problem 640. Getting logical indexes

This is a basic MATLAB operation. It is for instructional purposes.


Logical indexing works like this.

thresh = 4;
vec    = [1 2 3 4 5 6 7 8];
vi     = (vec > thresh)
vi =
       0     0     0     0     1     1     1     1

Once you have this TRUE FALSE vector (I call it vi: Valid Indices)

It can be used to get the values out:

big = vec(vi)
big =
       5     6     7     8

Given a vector, vec, and a value, v, return a binary vector that represents the indices where vector, vec, is equal to scalar, v.

Note, this works just as well with scalars and matrices.


To get the indices where this comparison is true, see this Cody problem.

Solution Stats

64.02% Correct | 35.98% Incorrect
Last solution submitted on Oct 24, 2016
Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

MATLAB Academy

New to MATLAB?

Learn MATLAB today!

Join the 15-year community celebration.

Play games and win prizes!

Learn more