## how to replace the element with random number based if statement

### Genz (view profile)

on 16 Oct 2019
Latest activity Commented on by sid Chen

on 17 Oct 2019

### Andrei Bobrov (view profile)

Helllo everyone
i have a problem to change element of array with iteration approach. refer to https://www.mathworks.com/matlabcentral/answers/8817-how-to-replace-the-elements-of-a-matrix-using-the-conditions-if-else , i have same problem but little different. for instance i have mut1 = [.11 .12 .13 .14 .15 .16 .17 .18 .19 .20] and constan number 0.5. i want to replace element of mut1 with 'random number between' if random number(rmi) < 0.5. so this is what iam doing.
mutC = zeros(size(mut1));
pm = 0.5;
for i = 1:numel(mut1)
rmi = rand(1,1)
rCm = rbC+(raC-rbC).*rand(1,1)
if rmi<pm
mutC = rCm
else
mutC = mut1
end
end
but the final result is always mutC = mut1. there is no number from rCm.
I will appreciate any help. thank you.

R2016b

### Andrei Bobrov (view profile)

on 16 Oct 2019
Edited by Andrei Bobrov

### Andrei Bobrov (view profile)

on 16 Oct 2019

mutC = mut1;
[m,n] = size(mut1);
pm = 0.5;
rmi = rand(m,n);
rCm = rbC+(raC-rbC).*rand(m,n);
for i = 1:numel(mut1)
if rmi(i) < pm
mutC(i) = rCm(i);
end
end
or
pm = .5;
mutC = mut1;
[m,n] = size(mut1);
rCm = rbC+(raC-rbC).*rand(m,n);
lo = rand(m,n) < pm;
mutC(lo) = rCm(lo);

Genz

### Genz (view profile)

on 16 Oct 2019
thank you for you fast reply sir. one more question sir. how i can store the random value "rCm'? because i have to submit 'rCm' value.
thank you.
Andrei Bobrov

on 16 Oct 2019
I'm fix.
Genz

### Genz (view profile)

on 16 Oct 2019
many thanks sir. 2 thumbs up..
GBU.

### sid Chen (view profile)

on 16 Oct 2019

The problem is
if rmi<pm
mutC = rCm
else
mutC = mut1
with these code, you replace the whole matrix, all the elements are replaced.
To avoid this, you need to replace only one elements step by step. Just add an subscipt 'i' to point the element to be repalced.
if rmi<pm
mutC(i) = rCm(i)
else
mutC(i) = mut1(i)

Genz

### Genz (view profile)

on 16 Oct 2019
when i run this code become error "index exceeds matrix dimensions"
sid Chen

### sid Chen (view profile)

on 17 Oct 2019
if rmi<pm
mutC(i) = rCm % change here, rCm is a number,not a matrix
else
mutC(i) = mut1(i)