Say you have two numpy arrays one, call it A = [x1,x2,x3,x4,x5] which has all the x coordinates, then I have another array, call it B = [y1,y2,y3,y4,y5].. How would one "extract" a set of coordinates e.g (x1,y1) so that i could actually do something with it? Could I use a forloop or something similar? I can't seem to find any good examples, so if you could direct me or show me some I would be grateful.
4 Answers
Not sure if that's what you're looking for. But you can use numpy.concatenate. You just have to add a fake dimension before with [:,None] :
import numpy as np
a = np.array([1,2,3,4,5])
b = np.array([6,7,8,9,10])
arr_2d = np.concatenate([a[:,None],b[:,None]], axis=1)
print arr_2d
# [[ 1 6] [ 2 7] [ 3 8] [ 4 9] [ 5 10]]
Once you have generated a 2D array you can just use arr_2d[i] to get the i-th set of coordinates.
Comments
import numpy as np
a = np.array([1, 2, 3, 4, 5])
b = np.array([6, 7, 8, 9, 10])
print(np.hstack([a[:, np.newaxis], b[:, np.newaxis]]))
[[ 1 6]
[ 2 7]
[ 3 8]
[ 4 9]
[ 5 10]]
Comments
As @user2314737 said in a comment, you could manually do it by simply grabbing the same element from each array like so:
a = np.array([1,2,3])
b = np.array([4,5,6])
index = 2 #completely arbitrary index choice
#as individual values
pointA = a[index]
pointB = b[index]
#or in tuple form
point = (a[index], b[index])
If you need all of them converted to coordinate form, then @Nuageux's answer is probably better
Comments
Let's say you have x = np.array([ 0.48, 0.51, -0.43, 2.46, -0.91]) and y = np.array([ 0.97, -1.07, 0.62, -0.92, -1.25])
Then you can use the zip function
zip(x,y)
This will create a generator. Turn this generator into a list and turn the result into a numpy array
np.array(list(zip(x,y)))
the result will look like this
array([[ 0.48, 0.97],
[ 0.51, -1.07],
[-0.43, 0.62],
[ 2.46, -0.92],
[-0.91, -1.25]])
pcontaining the first two elements of the arrays (x1,y1) you could use for instancep=(A[0],B[0])