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pythonnumpy
tattybojangler
tattybojangler

Reputation: 1073

Calculating distance between each consecutive element of an array

Let's say that I have the following array of numbers:

array([[-3 ,  3],
   [ 2, -1],
   [-4, -4],
   [-4, -4],
   [ 0,  3],
   [-3, -2],
   [-4, -2]])

I would then like to compute the norm of the distance between each pair of consecutive numbers in the columns, i.e.

    array([[norm(2--3), norm(-1-3)],
   [norm(-4-2), norm(-4--1)],
   [norm(-4--4), norm(-4--4)],
   [norm(0--4), norm(3--4)],
   [norm(-3-0), norm(-2-3)],
   [norm(-4--3)-3, norm(-2--2)])

I would then like to take the mean of each column.

Is there a quick and efficient way of doing this in Python? I've been trying but have had no luck so far.

Thank you for your help!

Upvotes: 0

Views: 1263

Answers (1)

Miriam Farber
Miriam Farber

Reputation: 19624

This will do the job:

np.mean(np.absolute(a[1:]-a[:-1]),0)

This returns

array([ 3.16666667,  3.16666667])

Explanation:

First of all, np.absolute(a[1:]-a[:-1]) returns

array([[5, 4],
       [6, 3],
       [0, 0],
       [4, 7],
       [3, 5],
       [1, 0]])

which is the array of the absolute values of the differences (I assume that by norm of a number you mean absolute value). Then applying np.mean with axis=0 returns the average value of every column.

Upvotes: 1

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