All Questions
34,526 questions
2
votes
1
answer
69
views
How to compute elementwise dot product of two 2D NumPy arrays [duplicate]
This script:
import numpy as np
a = np.array([[0, 1], [1, 1], [1, 0]])
b = np.array([[1, 0], [1, 1], [1, -1]])
dot = a[:, 0]*b[:, 0] + a[:, 1]*b[:, 1]
print(dot)
produces elementwise dot product of ...
- 8,265
2
votes
1
answer
104
views
Why the performance is bad if I use HashMap to solve Codility problem MinAbsSum?
Regarding the Codility problem MinAbsSum at https://app.codility.com/programmers/lessons/17-dynamic_programming/min_abs_sum/, the performance is bad if I use HashMap to solve the problem. I expect the ...
- 31
2
votes
2
answers
71
views
Pandas: Fill in missing values with an empty numpy array
I have a Pandas Dataframe that I derive from a process like this:
df1 = pd.DataFrame({'c1':['A','B','C','D','E'],'c2':[1,2,3,4,5]})
df2 = pd.DataFrame({'c1':['A','B','C'],'c2':[1,2,3],'c3': [np.array((...
- 289
-1
votes
0
answers
34
views
Efficiently Finding the Indices of the N Largest Values in a NumPy Array Without Sorting the Entire Array [duplicate]
I'm working with very large NumPy arrays (millions to billions of elements) and need to find the indices of the N largest values in the array. Using np.argsort() followed by slicing to get the last N ...
- 106
0
votes
1
answer
67
views
Apparently weird condition on inclusion of endpoint in np.arange() [duplicate]
The numpy.arange function takes the three parameters: start, stop, step (positional args.)
The default step is 1.
Throughout my entire Numpy experience, the last element of the resultant array is not ...
2
votes
1
answer
105
views
Why do these nearly identical functions perform very differently?
I have written four functions that modify a square 2D array in place, it reflects half of the square array delimited by two sides that meet and the corresponding 45 degree diagonal, to the other half ...
- 3,834
0
votes
1
answer
58
views
nums[:] = unique anyone please explain this line of code [duplicate]
class Solution(object):
def removeDuplicates(self, nums):
unique = []
for num in nums:
if num not in unique:
unique.append(num)
nums[:] ...
5
votes
1
answer
233
views
Optimizing LeetCode's "Minimum Pair Removal to Sort Array II" Solution to Prevent Time Limit Exceeded Errors
I am working on the LeetCode problem 3510. Minimum Pair Removal to Sort Array II:
Given an array nums, perform the following operation any number of times:
Select the adjacent pair with the minimum ...
- 59
4
votes
1
answer
171
views
Efficient and readable way to get N-dimensional index array in C-order using NumPy
When I need to generate an N-dimensional index array in C-order, I’ve tried a few different NumPy approaches.
The fastest for larger arrays but less readable:
np.stack(np.meshgrid(*[np.arange(i, dtype=...
- 393
2
votes
2
answers
68
views
Numpy- strange behaviour of __setitem__ of array
Say we have an array:
a = np.array([
[11, 12, 13],
[21, 22, 23],
[31, 32, 33],
[41, 42, 43]
])
a[[1, 3], [0, 2]] = 0
So we want to set zeros to 0th and 2nd element at both 1st and ...
- 397
-4
votes
0
answers
61
views
Save images to disk from array in python [duplicate]
I would like to also save the images in the array, I'm able to return them but not save them, I get AttributeError: 'Axes' object has no attribute 'array_interface'
import random
import matplotlib....
- 21
-5
votes
1
answer
53
views
Fastest and cleaner ways to insert, update, delete 2-dimensional array [duplicate]
I'm newbie in python language and have some prolem here. I have a list of name and score for example:
score = [['Andy', 80], ['John', 70], ['Diana', 100]]
I want to Delete or Update score based on it'...
- 365
1
vote
5
answers
99
views
Can I multiply these Numpy arrays without creating an intermediary array?
This script:
import numpy as np
a = np.linspace(-2.5, 2.5, 6, endpoint=True)
b = np.vstack((a, a)).T
c = np.array([2, 1])
print(b*c)
produces:
[[-5. -2.5]
[-3. -1.5]
[-1. -0.5]
[ 1. 0.5]
[ ...
- 8,265
0
votes
1
answer
22
views
elasticsearch query with Python lists returns "Can't get text on a START_ARRAY at 1:30"
I'm new with elastic (any also with python) but have some first success:
es = Elasticsearch(['http://localhost:9200'], basic_auth=('user', 'pw'))
query_body = {
"query": {
"...
1
vote
3
answers
122
views
numpy element-by-element subtract
I have two numpy 'arrays':
1st is a 2D array with shape (N, 2)
2nd is a 3D "matrix" with shape (N, M, 2) where M can be different from 0 to N-1
Code example
import numpy as np
a = np.array([...
- 28