how to replace the element with random number based if statement

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.

Answer 1

[Andrei Bobrov]

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]

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]

I'm fix.

[Genz]

many thanks sir. 2 thumbs up..

GBU.

Answer 2

[sid Chen]

Andrei Answer is very clear.

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]

when i run this code become error "index exceeds matrix dimensions"

[sid Chen]

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