selecting values from matrix

Hi everyones,

I explain my question with an example :

q2 is obtained from an equation

A=[r1 r2 r3;q1 q2 q3;k1 k2 k3];

I want to select proportional row values (r2 and k2).

what should I do?

Thanks.

Answer 1

[Star Strider]

Another way, especially if you don’t know where ‘r2’ is in the matrix, regardless of how large the matrix is:

A = [1:3; 4:6; 7:9];
r2 = 5;
[r,c] = find(A == r2);
other_values = setdiff([1:size(A,1)],r);
Result = A(other_values,c)

Result =
     2
     8

[Hamid]

this is good way, thanks.

because of matrix size in my code I'm gonna use an excel file instead of writing matrix.

what do you recommend?

[Star Strider]

My pleasure.

My code will only work for a matrix in your MATLAB workspace. It will not work for Excel files. You would have to read the matrix into your workspace with the xlsread function first.

[Hamid]

OK Thanks very much

[Star Strider]

My pleasure.

Answer 2

[the cyclist]

Here's one way:

idx = A(2,:)==q2;
values = A([1 3],idx);

[Hamid]

this is right but here is my real problem :

I don't know which q will be obtain and it's dependent on some equations.

after that I want chosen r and k individually.

thanks.

[the cyclist]

Maybe Star Strider's answer works for you? If not, then I would say you should start over with a new question, and fully specify the general problem.

[Hamid]

OK thanks