The 2D Array Index access, with step value
Question:
I have an array like:
a =np.array([[1,2,3,5,8,7,2,1,3,5,1,2,20,21],[3,8,3,9,8,7,10,1,3,5,1,2,20,21]])
requirement:
need to access index value with given step. For an example step value 3.
Only index value not an elements value.
Required Output:
[[0,3,6,9,12],[0,3,6,9,12]]
Answers:
Use a list comprehension to repeat the range for each row.
a =np.array([[1,2,3,5,8,7,2,1,3,5,1,2,20,21],[3,8,3,9,8,7,10,1,3,5,1,2,20,21]])
indexes = [list(range(0, a.shape[1], 3)) for _ in range(a.shape[0])]
You can do:
a = np.array([[1,2,3,5,8,7,2,1,3,5,1,2,20,21],[3,8,3,9,8,7,10,1,3,5,1,2,20,21]])
step = 3
indices = [np.arange(0, arr.size, step) for arr in a]
print(indices):
[array([ 0, 3, 6, 9, 12]), array([ 0, 3, 6, 9, 12])]
If you want lists instead of np arrays, just use .tolist() like:
[np.arange(0, arr.size, step).tolist() for arr in a]
I have an array like:
a =np.array([[1,2,3,5,8,7,2,1,3,5,1,2,20,21],[3,8,3,9,8,7,10,1,3,5,1,2,20,21]])
requirement:
need to access index value with given step. For an example step value 3.
Only index value not an elements value.
Required Output:
[[0,3,6,9,12],[0,3,6,9,12]]
Use a list comprehension to repeat the range for each row.
a =np.array([[1,2,3,5,8,7,2,1,3,5,1,2,20,21],[3,8,3,9,8,7,10,1,3,5,1,2,20,21]])
indexes = [list(range(0, a.shape[1], 3)) for _ in range(a.shape[0])]
You can do:
a = np.array([[1,2,3,5,8,7,2,1,3,5,1,2,20,21],[3,8,3,9,8,7,10,1,3,5,1,2,20,21]])
step = 3
indices = [np.arange(0, arr.size, step) for arr in a]
print(indices):
[array([ 0, 3, 6, 9, 12]), array([ 0, 3, 6, 9, 12])]
If you want lists instead of np arrays, just use .tolist() like:
[np.arange(0, arr.size, step).tolist() for arr in a]