Finding the center point between two points on a plane

Question

Challenge:

To take two points on the plane and figure out the position of the point that's a) on the line that connects them, and b) equally distant from each of the original points.

Example:

(0,0), (3,3) -> (1.5,1.5)

(-1,-1), (1,1) -> (0,0)

(-7,3), (2,-2) -> (-2.5,0.5)

(3, 1), (-5,9) -> (-1,5)

Rules:

• The input and output can be a tuple, array, list, or any other type of sequence.
• There must be two inputs, each representing a point.
• The output has to support floating point numbers.

Shortest solution in bytes wins.

Answer 1

Jelly, 7 2 bytes

-5 bytes (ha ha, yes I am an idiot) thanks to FryAmTheEggman!

+H

Takes two lists each of length d and returns one list of length d where d is the dimensions of the Cartesian space (question is posed for 2 dimensions, but should work for any d).

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How?

+H - Main link: a, b (lists of coordinates)
+  - add (vectorises across the dimensions)
 H - halve (vectorises across the result)

Answer 2

Mathematica, 4 bytes

Mean

Works on lists of vectors: for example, Mean[{{-7, 3}, {2, -2}}] returns {-5/2, 1/2}. (If the input consists of floating-point numbers, so will the output.)

Answer 3

Python 3, 39 35 bytes

lambda*x:[sum(a)/2for a in zip(*x)]

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Answer 4

Haskell, 22 19 bytes

zipWith$((/2).).(+)

Can be called with (zipWith$((/2).).(+)) (p1::[a]) (p2::[a]) where a is any type deriving Fractional. Works in arbitrary dimensions.

Answer 5

TI-BASIC, 8 bytes

.5(L₁+L₂

Takes input on List 1 and List 2. Works for all dimensions.

Answer 6

Julia 0.6, 13 bytes

(x->x/2)∘(+)

Answer 7

Common Lisp, 70 54 49 bytes

Thanks to @Julian Wolf for helping to save a bunch of bytes!

(defun f(a b)(mapcar(lambda(c d)(/(+ c d)2))a b))

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Answer 8

JavaScript , 30 bytes

valid for any number of dimensions

a=>b=>a.map((c,i)=>(c+b[i])/2)

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Answer 9

R, 22 bytes

As an unnamed function that takes 2 vectors as parameters. Simply returns the mean of input vectors the same as a lot of answers.

function(a,b)((a+b)/2)

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And 16 bytes using the pryr library

pryr::f((a+b)/2)

Answer 10

Python + NumPy, 18 bytes

lambda a,b:(a+b)/2

Works in two dimensions for points inputted as imaginary numbers, or (since OP specifies that inputs must be taken as sequences) in arbitrary dimensions for points inputted as NumPy arrays.

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Answer 11

Math.JS, 14 bytes

f(a,b)=(a+b)/2

Creates function f which takes 2 One Dimensional Matricies as input.

As expected, this just adds the two, then halfs the result.

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Answer 12

Julia, 13 bytes

a->b->(a+b)/2

Call with currying syntax, i.e. (a->b->(a+b)/2)([1,2])([3,4]).

Answer 13

Python + NumPy, 17 bytes

lambda a:sum(a)/2

A slightly less boring version of the other python answer. Takes args as 1 numpy array, containing both pairs.

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