Find an element of a matrix equal to a constant

Hi,

If B is a matrix i need to find the index of element that is equal to a constant c where the constant c is undoubtedly somewhere in the matrix.

I tried to do:

B(:,B(2,:)==c)

but there are some problems with logical operator ==

It returns me "Empty matrix"

Answer 1

[Matt Fig]

If you are looking for the linear index:

I = find(B==c);

If you are looking for the subscript index:

[I,J] = find(B==c);

I hope you are not experiencing a floating point issue???

Whenever I hear somebody say they cannot find a value that they just know is in an array, I wonder if they are not about to learn the joys of floating point arithmetic.

[cyberdyne]

I'm looking for subscript index but after i enter your code it retuns again:

Empty Matrix

[Walter Roberson]

Yup, see the link Matt posted about floating point issues.

[cyberdyne]

Great! The problem was it. Thanks.