how to find position of an element in a matrix which is present in another matrix?

I am having two matrix. Selected elements in one matrix is present as elements in another matrix. Now i need to find the position of selected elements in the original matrix.

For example:

a=[0.74 0.71 0.604 0.47 0.59 0.58 0.75];

b=[0.604 0.75];

Expected output:

c=[3 7]

I need to apply this problem to a larger n*m matrix.

[Stephen23]

Do not use ISMEMBER (unless you really know what you are doing with binary floating point numbers).

Use ISMEMBERTOL instead.

[ASHA PON]

Thank you for your reply.

Answer 1

[DGM]

a=[0.74 0.71 0.604 0.47 0.59 0.58 0.75];
b=[0.604 0.75];

% get the index of matches
% ainb are the indices of elements of a which are in b
% bina is a logical array describing which elements of b are in a
[bina ainb] = ismember(b,a)

bina = 1×2 logical array
   1   1

ainb = 1×2

3 7

% get the matched values
a(ainb)

ans = 1×2

0.6040 0.7500

Two things:

First, if you want to get row and column subscripts for use with a 2D array, you should be able to convert idx using sub2ind().

Second, for floating-point inputs, it may be a good idea to use ismembertol() instead of ismember()

[ASHA PON]

Thank you for your reply. This is what i needed.