MATLAB: How to find the index in array

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Dear all,

I have the following array A = [0;0;0;0;0;0;1;1;;0;0;0;0];

I want to find the right and left index of the 1's? In this case

Left_A = 7

Right_A = 8

In another situations, A = [0;0;0;0;0;0;1;0;0;1;0;0;0];

Left_A = 7

Right_A = 10

Any idea how to do that? Thank you very much.

Meshoo

Best Answer

Left_A = find( A == 1, 1 );
Right_A = find( A == 1, 1, 'last' );

Related Solutions

MATLAB: Finding matrix column index based on certain conditions

result = find(sum(A==1)==1 & sum(A==0)==(size(A,1)-1));

MATLAB: Find index of first zero searching from left first column first row, then find index of first zero searching from last column last row

MATLAB stores data column first in memory. Accessing your 2D array linearly follows this structure. Evaluate

 >> M(:)

and you will see a column vector that represents the content of the array read column per column. This means that you can FIND the linear index of these 0s using the 'first' (default) or 'last' options of FIND, by operating on M(:):

 >> M = randi( 10, 4, 5 ) > 5
 M =
  4×5 logical array
   1   1   1   1   0
   1   0   1   0   1
   0   0   0   1   1
   1   1   1   0   1
 >> linId = find( M(:) == 0, 1 )
 linId =
     3
 >> linId = find( M(:) == 0, 1, 'last' )
 linId =
    17

What remains is to convert linear indices back to subscripts, and you can do this using IND2SUB. For example:

 >> [r,c] = ind2sub( size( M ), find( M(:) == 0, 1, 'last' ))
 r =
     1
 c =
     5

Best Answer

Related Solutions

MATLAB: Finding matrix column index based on certain conditions

MATLAB: Find index of first zero searching from left first column first row, then find index of first zero searching from last column last row

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