how to replace the element with random number based if statement

Asked by Genz on 16 Oct 2019

Latest activity Commented on by sid Chen on 17 Oct 2019

3 views (last 30 days)

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.

0 Comments

Products

MATLAB

Release

R2016b

2 Answers

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Answer by Andrei Bobrov on 16 Oct 2019

Edited by Andrei Bobrov on 16 Oct 2019

Accepted Answer

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

pm = .5;
mutC = mut1;
[m,n] = size(mut1);
rCm = rbC+(raC-rbC).*rand(m,n);
lo = rand(m,n) < pm;
mutC(lo) = rCm(lo);

3 Comments

Genz 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 on 16 Oct 2019

many thanks sir. 2 thumbs up..

GBU.

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Answer by sid Chen on 16 Oct 2019

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)

2 Comments

Genz on 16 Oct 2019

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

sid Chen on 17 Oct 2019

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

Products

MATLAB

Release

R2016b

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