Calculating euclidean distances in a matrix
2 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
I have to a matrix n x 2 in which each row represent a point in a Cartesian space in X and Y. The distance I have to calculate is between a row and its follower so at the end I have an array (n-1) x 1. I ve coded a simply function but since n = 50 000 it takes a lot of time to compute. How to speed up the entire process?
That s my function:
function [Dist] = Distances(A)
n = length(A)
Dist = (n -1);
for i=1:n
if i == n
break
end
Dist(i,1)= sqrt((A(i+1,1)- A(i,1))^2 + (A(i+1,2)- A(i,2))^2)
i= i+1
end
0 commentaires
Réponses (2)
KSSV
le 16 Déc 2020
Modifié(e) : KSSV
le 16 Déc 2020
% demo data
n = 100 ;
A = rand(n,2) ;
dA = diff(A) ;
d = sqrt(sum(dA.^2,2)) ;
1 commentaire
Image Analyst
le 16 Déc 2020
This is what I'd do too. It's fast:
tic
n = 50000; % fifty thousand
xy = rand(n,2);
dxy = diff(xy);
d = sqrt(sum(dxy.^2,2));
toc
On my computer it takes 0.003 seconds for 50,000 rows.
Star Strider
le 16 Déc 2020
Example —
x = randi(99, 5, 2); % Create Matrix
d = pdist(x);
m = squareform(d);
The information you want are in the upper and lower diagonals of ‘m’, so:
Result = diag(m,1);
equivalently:
Result = diag(m,-1);
This is likely faster than an explicit loop, however I did not time it with a large matrix.
0 commentaires
Voir également
Catégories
En savoir plus sur Descriptive Statistics dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!