How to change 0 to 1 and update a matrix

Asked by Antonio Grivas on 21 Jun 2019

Latest activity Answered by Antonio Grivas on 22 Jun 2019

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b1 = [10; 20 ; 30 ; 40];
A = [0 20 0 10 ; 20 0 30 0 ; 0 30 0 10 ; 20 0 10 0];
s = size(b1);
x = randi([0 1],s)
G = [];
[ n m ] = size(x);
for i = 1 : n
    for j = 1 : m
    G(:,i) = x(:,j)
    a = find(G(: , i) == 0 , 1 , 'first')
    [x y] = size(G(:,i))
    for k = 1:y
        G(: , k) = 0;
        G(a , k) = 1
    end
    end
    i = i + 1;
    j = j + 1;
end

This prob wil work only the first time. I want the matrix to take a column, find where the first 0 is and change it to 1. Then proceed to the next line and do the same but keep the first column and not change it to 0s. Final solution must look like

(x changes randomly with 0 and 1 )

G =
   0     0     0
   1     0     0
   0     1     0
   0     0     1

I would appreciate any answer :)

5 Comments

Show 2 older comments

Antonio Grivas on 21 Jun 2019

I can do it in a 4x4 matrix by copying the same code 4 times but what if a matrix is 500x500 !!! final matrix G is always squared.

Stephen Cobeldick on 21 Jun 2019

@Antonio Grivas: Whenever I run your code it always returns this:

It is unclear how this output relates to your examples.

Please explain the logic of what you are trying to achieve.

Antonio Grivas on 21 Jun 2019

It is completely wrong. I don't know how to make it change the final result whick would be

1 0

0 1

0 0

1 0 0

0 1 0

0 0 1

0 0 0

1 0 0 0

0 1 0 0

0 0 1 0

0 0 0 1

I send the (without the wrong loop) answer where the program runs correctly only the first time

I suppose that i need a

for i = 1:size(whatever)

whatever(: , i) = 0

whatever(: , a) = 1

end

that sould be put somewhere to keep the previous results and not change it back to

and change the position of the 1 after adding a column

If you run it just check only the 1st time before it changes it back to

becomes

0 1

0 0

1 0

0 0

Then for some reason that i cannot see does not continue but gives

0 4

I am trying to be precise if i can to help you

Thank you

2 Answers

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Answer by Andrei Bobrov on 21 Jun 2019

Edited by Andrei Bobrov on 22 Jun 2019

Accepted Answer

n = numel(x1);
y1 = ~x1;
% if MATLAB >= R2016b
k = y1.*eye(n);
% if MATLAB <= R2016a
k = bsxfun(@times,y1,eye(n));
out = [x1, zeros(n,n-1)];
p = find(y1);
out(:,2:numel(p)+1) = k(:,p);

4 Comments

Show 1 older comment

Antonio Grivas on 21 Jun 2019

I will run this program as soon as i finish from work and go home.

Thanks in advance

Antonio Grivas on 21 Jun 2019

Problem with matrix dimensions at k = y1.*eye(n);

Andrei Bobrov on 22 Jun 2019

You use old MATLAB.

Replace this expression with the following:

k = bsxfun(@times,y1,eye(n));

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Answer by Antonio Grivas on 22 Jun 2019

Thank you very much

Matlab version 2016a (that was the problem)

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