MATLAB: Distance between one point and the next of a list of points

Question

Hi guys,

I have a list of points like this one:

XY = [0 0;

1 0;

2 0;

3 0;

0 -1;

1 -1;

2 -1;

3 -1];

disp(XY);

I would like to find a function that calculates the Cartesian distance between each point and its consecutive of this list.

Anyone can help me?

Thank you so much!

Answer 1

Try this:

XY = [0  0;
	1  0;
	2  0;
	3  0;
	0 -1;
	1 -1;
	2 -1;
	3 -1]
consecutiveDistances = sqrt((x(2:end) - x(1:end-1)) .^ 2 + (y(2:end) - y(1:end-1)) .^ 2)

You'll see

consecutiveDistances =

1

1

1

3.1623

1

1

1

Another nice function you might want to know about, if you have the Statistics and Machine Learning Toolbox, is pdist2(). You can use pdist2(XY, XY) tol give distances between every point and every point in a 2-D array:

XY = [0  0;
	1  0;
	2  0;
	3  0;
	0 -1;
	1 -1;
	2 -1;
	3 -1]
distances = pdist2(XY, XY)

You'll see:

distances =

0 1 2 3 1 1.4142 2.2361 3.1623

1 0 1 2 1.4142 1 1.4142 2.2361

2 1 0 1 2.2361 1.4142 1 1.4142

3 2 1 0 3.1623 2.2361 1.4142 1

1 1.4142 2.2361 3.1623 0 1 2 3

1.4142 1 1.4142 2.2361 1 0 1 2

2.2361 1.4142 1 1.4142 2 1 0 1

3.1623 2.2361 1.4142 1 3 2 1 0

The columns and row numbers refer to the row in your XY list. So for example, the element at Row 2, Column 3 of distances corresponds to the distance between point (row) 2 of your XY, and point (row) 3 of your XY. So you'd want to look at the diagonal one above the main upper left-to-lower right diagonal. You'll see it is the same list of numbers as consecutiveDistances.