get values from hough transform to calculate euclidean

RGB = imread('621.jpg');

I = rgb2gray(RGB);

BW = edge(I,'canny');

imshow(BW);

[H,theta,rho] = hough(BW);

figure

imshow(H,[],'XData',theta,'YData',rho,...

'InitialMagnification','fit');

xlabel('\theta'), ylabel('\rho');

axis on, axis normal, hold on;

hi, from the coding above, i get values in my workspace. The problem is I dont know which values (H, theta or rho) to use to calculate euclidean. Can someone help me?