MATLAB: Find function on specific row and column of an array.

Question

Hi,

I used find function in order to find row location of an array cell. To illustrate in an example:

A=magic(10)
A =
    92    99     1     8    15    67    74    51    58    40
    98    80     7    14    16    73    55    57    64    41
     4    81    88    20    22    54    56    63    70    47
    85    87    19    21     3    60    62    69    71    28
    86    93    25     2     9    61    68    75    52    34
    17    24    76    83    90    42    49    26    33    65
    23     5    82    89    91    48    30    32    39    66
    79     6    13    95    97    29    31    38    45    72
    10    12    94    96    78    35    37    44    46    53
    11    18   100    77    84    36    43    50    27    59
find(A(4:5,4)==21)
ans =
       1

What I wanted to get is in intersection of a row window and a specific column, I wanted to find a specific input's row location in the matrix. I expected to find the row number as 4, however I get 1. Find function thinks A(4:5,4) is a new array and gives locations accordingly.

Does anyone know how to get the true row location when I specify an mxn sub-matrix in a rxs matrix where r>m, s>n?

Thx,

JD

Answer 1

To find a submatrix in another matrix, use ismember:

m = magic(10)
subm = m(4:6, 3:8)
% c = normxcorr2(subm, m)
[ia, ib] = ismember(m, subm)