How to find the position of a number in an array?

If I have a vector, a = [7 8 8 2 5 6], how do I compute the positions of the value 8?

I expect 2 and 3 or (1,2) and (1,3).

Answer 1

[Walter Roberson]

You can use the “find” function to return the positions corresponding to an array element value. For example:

a = [7 8 8 2 5 6]; 
linearIndices = find(a==8) 
 
linearIndices = 
     2     3 

To get the row and column indices separately, use:

[row,col] = find(a==8) 
 
row = 
     1     1 
 
col = 
     2     3 

If you only need the position of one occurrence, you could use the syntax “find(a==8,1)”. You can also specify a direction if you specifically want the first or last occurrence, such as “find(a==8,1,’first’). For more information on these options, see “find”.

Answer 2

[Bhagyesh Shiyani]

what if i want both 8 positions, any code?

[Florian Reinbold]

Hi Bhagyesh

i would suggest this one:

[val, idx] = find(a==8);

It seems to make a great job! :)

Cheers

Florian

[Walter Roberson]

This will not return value and index, it will return row and column numbers.

Answer 3

[Ujjawal Barnwal]

a = [7 8 8 2 5 6];

position = find(a==8)