Create a new numpy array with values based on coordinates and external variables

Question

Suppose I have a function that receive 3 parameters:

def foo(x, y, fac):
  return x * y * fac

How do I create a 2D numpy array, who's values will be the result of the above function when the parameters are the new array own x, y values?

Can you provide example of the input array? Not sure what you are trying to do. — Marcin
– Marcin, Commented Feb 13, 2015 at 6:50

ssm · Accepted Answer · 2015-02-13 07:58:28Z

1

Numpy already has a function called meshgrid. You would say:

x = np.array([1,2,3])
y = np.array([4,5,6])
X, Y = np.meshgrid(x, y)
result = foo(X, Y, 0.03)

answered Feb 13, 2015 at 7:58

ssm

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physicalattraction · Accepted Answer · 2015-02-13 07:09:34Z

0

I guess this is what you want to accomplish. I don't know if you can speed it up by getting rid of the loop though.

import numpy as np

def foo(x, y, fac):
    return x * y * fac

def make2dmatrix(a, b):
    C = np.zeros(shape=[a.size, b.size])
    for i in range(a.size):
        C[i, :] = foo(a[i], b, fac=0.5)
    return C

if __name__ == '__main__':
    a = np.array([1, 2, 3])
    b = np.array([2, 3, 4])
    print (make2dmatrix(a, b))

Outcome

[[ 1.   1.5  2. ]
 [ 2.   3.   4. ]
 [ 3.   4.5  6. ]]

answered Feb 13, 2015 at 7:09

physicalattraction

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1 Comment

eumiro Over a year ago

range and numpy within one method are usually not an optimal match.

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