Get distance between adjacent array cells

Hello everyone,

I have a little problem calculating a velocity from a distance matrix. I do have the time array already.

My distance matrix looks as following:

dist=[x_coord1, y_coord1;
      x_coord2, y_coord2;
      ....];

The coordinates are absolute, and I need the relative distance between the current coordinates and the previous one.

So, my vector should look like this:

newdist=[pdist2([x_coord2,y_coord2],[x_coord1,y_coord1]);
         pdist2([x_coord3,y_coord3],[x_coord2,y_coord2])
         ......];

But instead pdist2 gives a vector with the distance of every possible combination of cells.

My questions(in my opinion at least):

1. Are there any functions which give me what I want immediately; or if this is not the case

2. Is there a way to decipher the pdist2 vector and get the correct values?

Thanks for reading this long post and helping :)

Kind regards, Dries van Roovert

Answer 1

[Dries van Roovert]

For anyone interested in the answer:

PairwiseDist=squareform(pdist(dist,'euclidean'));
RelativeDist=diag(PairwiseDist,-1);

You'll get the distance from coord 2 to 1, coord 3 to 2, ... and so on in a vector.

Cheers

Answer 2

[Jan]

v = diff(dist, 1, 1);

Perhaps:

v = sqrt(sum(v .* v, 2));

[Dries van Roovert]

I need the euclidean distance between the [x1,y1] and [x2,y2]. not just the distance between x1 & x2 and y1 & y2.

[Dries van Roovert]

That's not it either, on every row of the solution array should be the distance between the current coordinates and the previous.

%pdist2 is a function calculating distance between data sets
row 1 = pdist2([x2,y2],[x1,y1],'euclidean')
row 2 = pdist2([x3,y3],[x2,y2],'euclidean')