find and print values ​​from matrix

Hello everyone ,

works: 1 2 3 4 5 6

A1 3 1 2 2 3 1

A2 2 3 3 1 2 3

Can I find the value 2 in each row in the matrix given above and print the job number in another matrix?

Example: I found 2 values in row A1 in the given matrix. These are the 3rd and 4th jobs. I need to print these jobs in a matrix like below.

Works: 2

3

4

Answer 1

[Voss]

% given matrix with three rows:
M = [ ...
    1   2   3   4   5    6; ...
    3   1   2   2   3    1; ...
    2   3   3   1   2    3];
% value to look for in the second row of M:
val = 2;

% find the indices where val is in the second row of M:
idx = find(M(2,:) == val);

% output is val followed by those indices, all together in a column vector:
output = [val; idx(:)]

output = 3×1

2 3 4

[Esra Demirbilek]

Hello again;

Works: 5 8 9 15 7 12

A1: 1 3 2 3 1 2

A2: 3 2 1 1 2 3

Looking at the matrix structure given above, I want to print jobs with the value 3 in row A1 in another matrix. how can I do it?

Example for A1 ;

new matrix: 8

15

[Voss]

Works = [5   8   9  15   7  12];
A1    = [1   3   2   3   1   2];
A2    = [3   2   1   1   2   3];

result = Works(A1 == 3).'

result = 2×1

8 15

This uses what is called logical indexing:

https://www.mathworks.com/matlabcentral/answers/129-how-does-logical-indexing-work

https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

If Works, A1 and A2 are rows of a matrix, it works the same but you have to specify the row number instead of referring to the different variables:

M = [5   8   9  15   7  12; ...
     1   3   2   3   1   2; ...
     3   2   1   1   2   3];
result = M(1,M(2,:) == 3).'
% ^^^^^^                 result is ...
%        ^^^^            elements from row 1 of M ...
%            ^^^^^^      where row 2 of M ...
%                   ^^^^ is 3

[Esra Demirbilek]

thank you

[Voss]

You're welcome!