how to calculate the indices's distance of a vector using the data of a matrix?

Question

vinicius lanziotti 2017-12-7

回答： Honglei Chen 2017-12-7

something like this:

% Distance Matrix:

d=[0 10 20 30 40; 10 0 50 60 70; 20 50 0 80 90; 30 60 80 0 100; 40 70 90 100 0];

% Positions Vector:

x = [1 2 3 4 5];

I want the distances traveled from one element to the other of the vector, using the indices d (i, j) of the distance matrix.

for exemple: x = [1 2 3 4 5];

1->2 it's equal the distance of element d(1,2) or d(2,1) of distance matrix.

2->3 it's equal the distance of element d(2,3) or d(3,2) of distance matrix.

In the end, returns the traveled distance of the vector x = [1 2 3 4 5];

So:

distance = (1->2) + (2->3) + (3->4) + (4->5)

PS. THE VECTOR IS GENERIC.

Answer 1

Honglei Chen 2017-12-7

Not sure if I missed anything but looks to me this can be done by

sum(d(sub2ind(size(d),x(1:end-1),x(2:end))))

HTH