convering degrees to radians inside an array

Question

I have an array A,

array([[ 1,  2, 25],
       [ 3,  4, 23],
       [ 2,  6, 55],
       [ 9,  7, 78],
       [11,  5, 47]])

I changed the last column of the array, supposedly degree values (25,23,55,78,47) to radians.

its quite easy to do it, I did:

A_rad[:,2] = np.pi/180 *A[:,2]

you can also use np.radians, the output is:

    array([[ 1,  1,  0],
           [ 2,  3,  0],
           [ 3,  2,  0],
           [ 9,  5,  0],
           [11,  3,  0]])

surely the last columns need to be changed, but not to zeros, i changed also the data type from int to float, the output were only 0., I need at least 3 decimals places in order to solve my problems.

The last column should give output as array([0.4363, 0.4014, 0.9599, 1.3614, 0.8203]). The thing is python doesn't save the decimals in the memory, so even if i multiply it always gives 0.

Is python able to do it?

any ideas.

Answer 1

You should cast your array to float:

import numpy as np

A = np.array([
    [ 1,  2, 25],
    [ 3,  4, 23],
    [ 2,  6, 55],
    [ 9,  7, 78],
    [11,  5, 47]
]).astype(float)

A[:,2] = np.radians(A[:,2])

print(A)

This produces:

[[ 1.          2.          0.43633231]
 [ 3.          4.          0.40142573]
 [ 2.          6.          0.95993109]
 [ 9.          7.          1.36135682]
 [11.          5.          0.82030475]]

BTW: Instead of casting, you could also define the data type during initialization like so: A = np.array([...], dtype=float)