I am writing a code for circular convolution and now I am stuck at position where I need to create circular shift matrix can anyone help me to do this using python or numpy
I want to shift this matrix circularly [1, -1, 2, 0]
I want matrix like,
[ 1, -1, 2, 0]
[ 0, 1, -1, 2]
[-2, 0, 1, -1]
[-1, -2, 0, 1]
code:-
https://drive.google.com/file/d/16XNJ7Q5Iwdlg6Ouz8HU8PgW17xCd1gTp/view?usp=sharing
when you shift by n
you take last n
elements and put then in the front side of the list and that is l[len(l)-n:]
. And remaining 0 to len(l)-n-1
elements you put at the end and that is l[0:len(l)-n]
def shift(l,n):
return l[len(l)-n:] + l[0:len(l)-n]
output = []
m = [1, -1, 2, 0]
for i in range(4):
output.append(shift(m, i))
print(output)
# [[1, -1, 2, 0],
# [0, 1, -1, 2],
# [2, 0, 1, -1],
# [-1, 2, 0, 1]]
As suggested in a duplicate, collections.deque.rotate (builtin library) or numpy.roll (more efficient 3rd-party library) is almost-certainly what you're looking for!
>>> from collections import deque as Deque
>>> d = Deque([1, -1, 2, 0])
>>> d
deque([1, -1, 2, 0])
>>> d.rotate(1)
>>> d
deque([0, 1, -1, 2])
>>> import numpy as np
>>> arr = np.array([1, -1, 2, 0])
>>> np.roll(arr, 1)
array([ 0, 1, -1, 2])
>>> np.roll(arr, 2)
array([ 2, 0, 1, -1])
NOTE that the deque mutates the original collection, while numpy.roll returns a rotated copy
You can create a single DataFrame by assembling each possible roll for the length of the array, though you may find it's more efficient to calculate the rolls when you need them
>>> arr = np.array([1, 2])
>>> pd.DataFrame([np.roll(arr, roll_index) for roll_index in range(len(arr))])
0 1
0 1 2
1 2 1
>>> arr = np.array([1, -1, 2, 0, 9])
>>> pd.DataFrame([np.roll(arr, roll_index) for roll_index in range(len(arr))])
0 1 2 3 4
0 1 -1 2 0 9
1 9 1 -1 2 0
2 0 9 1 -1 2
3 2 0 9 1 -1
4 -1 2 0 9 1
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