Accessing coordinates within multidimensional arrays - python

Question

I am looking to put the x and y values of the coordinate grid into their own separate arrays in order to perform functions such as Pythagoras etc. Here's my code below.

x1d = np.linspace(-xlen,xlen,res)
y1d = np.linspace(-ylen,ylen,res)
from itertools import product
coordinates = list(product(x1d, y1d))
xcoord = coordinates[:][:][0]

print np.shape(coordinates), np.shape(xcoord), coordinates

I get that the below code will give me

coordinates = [[x1,y1],[x2,y2],...,[xn,yn]].

How would one go about extracting the following arrays?

xcoord = [x1,x2,...,xn]
ycoord = [x1,x2,...,xn]

Is this the right solution for generating a 2D grid of points where I can perform functions upon each individual x,y point, assigning a resultant value to that point?

Thanks!

The code you have will not do what you think it will. Take a look at the following: stackoverflow.com/questions/11144513/… — user2357112
– user2357112, Commented Nov 28, 2013 at 22:37

pandita · Accepted Answer · 2013-11-28 22:35:30Z

2

You could also use itertools to get your x and y values:

import itertools
x,y=itertools.izip(*coordinates)

# x=(x1,x2,...,xn)
# y=(y1,y2,...,yn)

In regards to the grid, have a look at numpy's meshgrid which could be useful for you. You can use it like so (taken from the example on the linked website):

x=np.arange(-5,5,.1)

y=np.arange(-5,5,.1)

xx,yy=meshgrid(x,y,sparse=True)

xx,yy=np.meshgrid(x,y,sparse=True)

z = np.sin(xx**2 + yy**2) / (xx**2 + yy**2)

h = plt.contourf(x,y,z)

Numpy's meshgrid

edited Nov 28, 2013 at 22:35

answered Nov 28, 2013 at 7:28

pandita

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3 Comments

Raptor Over a year ago

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post.

pandita Over a year ago

@Shivan Why not? If I do x,y=itertools.izip(zip(range(10),range(10,20)) i get x=(0,1,2,...) and y=(10,11,...) which I think is what has been asked...

pandita Over a year ago

@Shivan I added some words around it... I hope this is clearer now

aIKid · Accepted Answer · 2013-11-28 08:47:54Z

0

Treating it as a normal list, you can use a list comprehension:

xcord, ycord = [e[0] for e in coordinates], [e[1] for e in coordinates]

Hope this helps!

edited Nov 28, 2013 at 8:47

answered Nov 28, 2013 at 7:08

aIKid

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