I want to do a calculation through a function, which is related to kx and ky. kx and ky are two 2D arrays. How can I use python to do this?
Thank you!!!
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1Any reason why you don't just loop over x and y and set your new matrix element to (kx[x][y]/(kx[x][y]**2 + ky[x][y] ** 2)) ?DJSchaffner– DJSchaffner2020-01-15 23:16:32 +00:00Commented Jan 15, 2020 at 23:16
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1 Answer
The de-facto standard package to do array math in python is numpy. So install the numpy package and then you'd do
import numpy as np ## Pretty much everyone imports numpy as np, so might as well.
def my_function(kx, ky):
return kx / (kx**2 + ky**2)
kx = np.array([[1, 2, 3], [1, 2, 3], [1, 2, 3]])
ky = np.array([[1, 1, 1], [2, 2, 2], [3, 3, 3]]) # Well we could also just have said ky = kx.T for the transpose, I guess.
output = my_function(kx, ky)
Note that math operations on numpy arrays are typically applied element-wise, so kx**2 just squares each element of kx individually, which is what you want here. For matrix-multiplication type squaring you'd do something like kx.dot(kx).
I assume your arrays kx and ky are just random examples; otherwise, there's more efficient ways to generate them than writing them out like this.
Of course nothing is wrong with the other posted solutions that use plain python objects and for loops, but for larger arrays you can expect numpy to be much more efficient.
4 Comments
Joanne
Actually I need more complex arrays, such like a 7X7 array. The value in each rows are the same, [1,2,3,4,5,6,7] ,[1,2,3,4,5,6,7] ,[1,2,3,4,5,6,7] ,[1,2,3,4,5,6,7] ,[1,2,3,4,5,6,7] ,[1,2,3,4,5,6,7] ,[1,2,3,4,5,6,7]. Is there any function like np.linespace? So that I can set the start number, end number, and the space? linespace(start, stop, num)
cadolphs
And would it look like "1, 2, 3, 4, 5, 6, 7" row-wise for the first one and column-wise for the second one?
cadolphs
There's both
linspace and arange. In this case you probably want arange(1, 8). And then there are helper functions that turn this 1d array into two 2d ones, such as meshgrid if I recall correctlyJoanne
Understand~ Thank you very much.