How to find the top 10% value of the matrix?

HI,

I have a 10x10 matrix and the value is random

How do I find the the top 10% value of the matrix?

ex: if the value is 1~100,I want to get the answer is 90~100

Thanks~

[Jan]

Because I assume that this is a homework question, please explain, what you have done so far and ask a specific question about the occurring problems.

Answer 1

[Sean de Wolski]

x = the_matrix;
[~,idx] = sort(x(:));
y = x(idx(1:10));

Answer 2

[TG]

To select the top 10% of a matrix, take the total number of values and multiply by .1. Then sort and extract as in the accepted answer above:

[m n] = size(X); %where X is your matrix
TN = m*n;
TTP = TN*.1;

TTP = ceil(TTP); %round in case TN is an odd number and TTP is not an integer 
                  (i.e. 5x5 = 25, 25/10 = 2.5)

For matrices, 'sort' sorts each column individually, so first covert the matrix into a single vector, then sort:

VX = X(:);               %places values in single column
[val,ind] = sort(VX, 'descend');
y = VX(ind(1:TTP));

You can play around with the 'ind' variable and the code to locate these values in the original matrix.