How to randomly sample a value multiple times from data

Hi.

I have a dataset containing x, y, z coordinates with which I can draw a 2D figure as below:

What I want to do is to sample a value randomly multiple times (e.g 2,000 times) from Z values within the black circle (ind = (Y-65).^2 + (X-85).^2 <= 45^2;). Z values within the circle range from 0 to 65. Then I'd like to analyze the probability that the sampled values are greater (or less) than 15.

Could you help me with this task?

Thanks in advance.

Answer 1

[KSSV]

Let x,yz be your data. (May be column or matrix)

idx =  (X-85).^2 + (Y-65).^2  <= 45^2; 
% get the required indices data of (x,y)
x1 = x(idx) ; y1 = y(idx) ;  % this will be a column matrix 
n = length(x) ; % total points 
% select random 100 random points in (x,y) 10 times 
for i = 1:10
    id = randi(n,1,100) ;  % you can keep your number less than n 
    xi = x(id) ; 
    yi = y(id) ; 
    % do what you want 
end