how to find out how many times a number apears in a 2D matrix ? which function to use?

Hey,

how can I find how many time a numbers appears in an 2D matrix for example:

If I have a matrix

x=[1,3,4;2,2,1;2,2,1]

number 2 appears 4 times

numger 1 appears 2 times

number 3 appears 1 time

Desired output:

22    1   3
22    1

[Image Analyst]

You can't have an array with ragged right edge. Arrays must be rectangular. What do you want in the space below the 3? Or else you could have a 1-by-3 cell array, ca where

ca{1} = [2, 2; 2, 2];
ca{2} = [1;1];
ca{3} = 3;

Is that what you want?

Anyway, 1 appears 3 times, not 2 times, and what about 4? Why is 4 not in your desired output?

Answer 1

[madhan ravi]

n=2; % number to be tested 
nnz(ismember(x,n))

[aya qassim]

thank you,

But if I only have the matrix as an input (I don't have an input fot the number ) , how can I find out how many time a number apprears?

[madhan ravi]

Try the below , a in result represent unique numbers and the corresponding histc() shows how many times they occur in the matrix:

a = unique(x);
result = [a histc(x(:),a)]

Answer 2

[Walter Roberson]

[ux, ia, ic] = unique(x);
output = [ux, accumarray(ic, 1)]