how do i get the top 10 percent of the matrix value

so basically I have a matrix of 20x20. I need to extract out the top 10 percentage of the value and put it into a vector form. how should I do it?

Answer 1

[Star Strider]

This seems to do what you want:

M = randn(20);                                      % Create Data
Ms = sort(M(:),'descend');                          % Sort Descending
Result = Ms(1:ceil(length(Ms)*0.1));                % Desired Output

[jun xian ng]

Thank you, it works! But would you mind explaining what is 1:ceil for in the result

[Star Strider]

My pleasure.

The ‘Ms’ vector sorts in descending order, that is from higher to lower values, so that the highest value in in the ‘Ms’ vector is the first element, ‘Ms(1)’. Taking the highest 10% then goes from 1 to the highest value (using the ceil or ‘ceiling’ function) given by the length of the vector divided by 10. The idea is that it will include at least the top 10% in the event that the multiplication by 0.1 results in a fractional value. (It doesn’t here, but there are floating-point approximation errors that could result in 400/10 not being exactly 40, so the ceil function corrects for that possibility.)

[jun xian ng]

oh, I see. I get it now. Thanks alot

[Star Strider]

My pleasure.

Answer 2

[Walter Roberson]

V = sort(YourMatrix(:), 'reverse');
Top10 = V(1:ceil(end/10));