Distance between one point and the next of a list of points?

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!

[darova]

Do you have any ideas?

Answer 1

[Image Analyst]

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.

Answer 2

[Sriram Tadavarty]

Hi Marco,

You can use the pdist and pdist2 functions in the Statistics Toolbox

XY = [ 0 0; 1 0; 2 0; 3 0; 0 -1;1 -1;2 -1;3 -1];
disp(XY)
pdist(XY) % THis will provide all the distances with all the combinations

Hope this helps.

Regards,

Sriram