All Questions
348 questions
5
votes
1
answer
110
views
Efficient way to delete columns and rows from a numpy array using slicing and not np.delete
Would it be possible given an array A, bad row indices and bad column indices to use slicing to make a new array that does not have these rows or columns?
This can be done with np.delete as follows:
...
- 107
1
vote
0
answers
55
views
Why is an array variable not getting updated unless assigning to [:]? [duplicate]
I was solving this leetcode problem of rotating the array right by k places and this is the function I wrote in Python:
class Solution:
def rotate(self, nums: List[int], k: int) -> None:
...
- 29
-3
votes
1
answer
103
views
How to Slice Multi Dimensional Array?
Dipping my toes into multi dimensional array slicing in Python and am hitting a wall of confusion with the following code
# Example 2D array
matrix = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9]
]
# ...
- 301
1
vote
1
answer
60
views
How to split an array using its minimum entry
I am trying to split a dataset into two separate ones by finding its minimum point in the first column. I have used idxmin to firstly identify the location of the minimum entry and secondly iloc to ...
- 25
1
vote
1
answer
78
views
Adding numpy arrays to cells of a pandas DataFrame depends on initialisation
I was trying to add a list of numpy arrays as elements to the pandas DataFrame:
DataFrame
using:
df.loc[df['B']==4,'A'] = [np.array([5, 6, 7, 8]),np.array([2,3])]
Whether or not this is allowed seems ...
- 13
0
votes
2
answers
129
views
Extract multiple roi's from np array using indices ranges without loops
I have a numpy array of shape 640 x 480: np.ones((640, 480)), and I have a min, max ranges for the rows, columns:
u_min=[497, 157, 493, 137, 567]
v_min=[ 36, 46, 208, 412, 418]
u_max=[502, 162, 498,...
- 304
1
vote
2
answers
84
views
Shapes of arrays obtained by mixed basic and advanced indexing in NumPy ndarray
Here is the code:
import numpy as np
x = np.arange(2*32*32*8*16)
x = x.reshape(2, 32, 32, 8, 16)
print("x-shape=", x.shape)
y = x[0, 3:5, 8:10, [1, 2, 3, 4, 5], :]
z = x[0][3:5, 8:10, [1, ...
- 11
1
vote
1
answer
39
views
How do I slice a 2D numpy array using another 2D numpy array that contains indices?
I have a sparse matrix A that is of size (3000,3000), and I have another matrix B that is of size (83068, 2) that contains the indices of the non-zero elements of A.
Is it possible to get a resulting ...
- 45
0
votes
1
answer
120
views
Select some specific columns in a 4D Numpy array
I'm trying to select a specific number of columns in a 4D array but apparently the way to do this is different compare to 3D arrays, example:
numpy_vector = np.arange(0,120,dtype=np.int8)
numpy_tensor ...
0
votes
1
answer
82
views
Can you slice a numpy 2D array with start and stop rules not at an index but at values greater than 1?
I have turned a geotiff LiDAR elevation surface into a numpy array by the below code:
example_array = np.array(geotiff_surface)
The array is hundreds of values by hundreds of values but could be ...
- 69
0
votes
1
answer
78
views
NumPy Nearest Neighbor Line Fitting Across Moving Window
I have two two-dimensional arrays loaded into NumPy, both of which are 80i x 80j in size. I'm looking to do a moving window polyfit calculation across these arrays, I've nailed down how to conduct the ...
- 431
1
vote
1
answer
60
views
How to find the maximum/minimum offset in np.diagonal()?
I want to get back all the diagonals of a numpy matrix in the form of a list and np.diagonal() does that but slice notation doesn't work on it.
I tried using slice notation, thinking by just putting a ...
- 13
2
votes
1
answer
707
views
How to use tuples as slice start:end values [duplicate]
I need to slice array with arbitrary dimensions by two tuples. I can use slicing, such as a[1:3, 4:6]. But what do i do if 1,3 and 4,6 are tuples?
While a[(1, 3)] works, I tried a[(1, 3), (4, 6)] and ...
- 668
0
votes
1
answer
316
views
xarray dataset extract values select
I have a xarray dataset from which I would like to extract points based on their coordinates. When sel is used for two coordinates it returns a 2D array. Sometimes this is what I want and it is the ...
- 2,406
-1
votes
2
answers
81
views
Masking an array
I am trying to mask an array (called dataset) in python:
The array has the following size (5032, 48, 48). Basically these are 5032 48x48 images. But some of the images may not contain any data, so ...
