## how to replace values of a matrix, if another matrix meet certain conditions?

### Alecd (view profile)

on 4 Apr 2017
Latest activity Commented on by Joseph Cheng

### Joseph Cheng (view profile)

on 4 Apr 2017
Hello
so I have a matrix A=[20 17 18 24, 12 22 27 11, 30 10 15 23, 28 20 14 11]
and a matrix B filled with zeros, of the same size (4x4).
I want to say that if the values of A are bigger than 18, then change the values in matrix B. Also taking into account the position of the elements, so for example the first element A(1,1) is bigger than 18, then B(1,1) will change to 1.
Edit: What if I have 3 matrixes, and the matrix B. So I want to say that if the values in matrix A are bigger than 18, and the values in matrix C are bigger than 10 and the values in matrix D are bigger than 30, then in Matrix B, change from 0 to 1, the element that meet the three conditions.

### Joseph Cheng (view profile)

on 4 Apr 2017
Edited by Joseph Cheng

### Joseph Cheng (view profile)

on 4 Apr 2017

i may be over simplifying it but doesn't the greater than (>) inequality just do it?
A=magic(5)
B=A>18

Alecd

### Alecd (view profile)

on 4 Apr 2017
What if I have 3 matrixes, and the matrix B. So I want to say that if the values in matrix A are bigger than 18, and the values in matrix C are bigger than 10 and the values in matrix D are bigger than 30, then in Matrix B, change from 0 to 1, the element that meet the three conditions.
Joseph Cheng

### Joseph Cheng (view profile)

on 4 Apr 2017
at this point my point stands and you should look up how to use logical operands https://www.mathworks.com/help/matlab/logical-operations.html if you are familiar with what the terms AND, OR, XOR, NOR, etc mean
Joseph Cheng

### Joseph Cheng (view profile)

on 4 Apr 2017
such that
magic(5)>10 & magic(5)<20
so the first part is highlighting with 1's which are greater than 10, second half which are less than 20. then the & is saying which positions are both 1s.