Select values in one column based on entries in another column

Hi.

I looking for a way to read values in one column based on the entries in qnother column,

For example in the attached array A, the first entry in the first column is -3.14, here I would like to read all the correponding entries in the third column whichever got -3.14 in the first column..

Answer 1

[Arif Hoq]

load matlab
[idx]=find(A(:,1)==-3.14) 
B=A(:,3); % third column
Output=B(idx);

[Turbulence Analysis]

Thanks, it is perfect

[Arif Hoq]

my pleasure

Answer 2

[Arthur Reis]

You can use a logical mask. For example (using two vectors, but it is easily adaptable for your case with arrays with many columns):

A = [1; 2; 3; -3.14; 4; -3.14];

A =

1.0000
2.0000
3.0000
-3.1400
4.0000
-3.1400

>> A_mask = (A==-3.14) % also works with <, >, >=, <=.....

A_mask =

6×1 logical array

0
0
0
1
0
1

>> B = ['a'; 'b'; 'c'; 'd'; 'e'; 'f']

B =

6×1 char array

'a'
'b'
'c'
'd'
'e'
'f'

>> B(A_mask) %passing a logical array as indexes will return every 'true' element
ans =

  2×1 char array

    'd'
    'f'