All Questions
19,923
questions
0
votes
1
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40
views
numpy giving wrong matrix results?
I am doing some matrix calculations and I am getting some wrong values.
import numpy as np
np.set_printoptions(formatter={'float': lambda x: "{0:0.2f}".format(x)})
#deltaT
arr1 = np.array([[...
- 11
1
vote
2
answers
83
views
Analogue of numpy indices for lua multidimensional array
In numpy any ndarray can be accessed by specifying a tuple of integers. So if we build an array with arbitrary dimensions and populate it using a formula that is based on the indices of an element, ...
- 180
-4
votes
0
answers
47
views
How does np.s_[86:87, 86:87] work? What do the parameters mean?
I have code where I take latitude, longitude, and height from a landing site on the moon. I get all my data but after I slice it all my data is gone. I don't really know how to use the parameters for ...
0
votes
0
answers
19
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Abstracting and generalizing spectogram function that accept sample_rate from the wavelet function and arbitrary signal
I'm trying to understand wavelet transform from scratch, that's why I don't want use any libraries/packages except numpy and matplotlib.
Import
import numpy as np
import matplotlib.pyplot as plt
...
0
votes
1
answer
53
views
Self differencing function for 2D numpy array (correlation?)
I have a 2D array mat of shape ~ (3000, 5). Now I want to subtract every column from the others and ignore the self subtraction. This is what I have right now and what works. I just want a more ...
- 99
0
votes
1
answer
56
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Efficiently recalculating dependent values in real-time data streams using NumPy in Python
I'm currently working on a real-time data processing system for financial securities, where I need to perform calculations as soon as new data comes in. Each financial security has multiple data ...
- 181
0
votes
3
answers
73
views
Numpy Unique - how to make array with counts?
So, basically, I have a txt file like this:
I read it and this is my code:
name_k, let_k = np.loadtxt(path + 'known_mass_period.txt', skiprows = 1, unpack = True, usecols = (0,1), dtype = str)
m_k, ...
1
vote
2
answers
67
views
create polars array series sharing data with numpy array, with unpredictable offsets
I'm working with "records" that are represented by ~1,000 sample arrays. I have millions of these records, so they take up a fairly significant amount of memory, often exceeding what is ...
- 2,376
1
vote
2
answers
73
views
How can I set a specific value on an array (matrix) of booleans per True/False without using loops in python?
I am trying to make two random generated matrices mat1 and mat2 with random integer values between 0, 255 and check which cells are equal.
and I know this much
import numpy as np
mat1 = np.random....
- 13
1
vote
2
answers
90
views
Create new matrix with sum of all n*n submatrixes sum without using loops
I have a starting array (a) and I'm using loops to create a new matrix (b) where every element represents the sum of every unique subarray n*n (0+1+5+6=12, 1+2+6+7=16, ...). Can I achieve the same ...
- 13
0
votes
1
answer
68
views
How to Generate a Random Complex Symmetric Unitary Matrix in Python?
I am trying to optimize a complex symmetric unitary matrix
𝐴 with dimensions N*N using Python.
First of all, how to generate matrix 𝐴 that should satisfies the two conditions:
𝐴=𝐴^{T} (...
0
votes
2
answers
48
views
Performance degradation of matrix multiplication involving integer-array-indexed arrays in numpy
I'm working on a project where I have to perform some row and/or column permutaion before (broadcasted) matrix multiplication. While the implementation is straightforward with numpy, I noticed that ...
- 33
0
votes
1
answer
59
views
In NumPy arrays, is there a syntax to set a value in the last dimension based on the first dimension?
I've Googled and asked ChatGPT and looked through NumPy docs and can't find any way to do this, so thought I'd ask here.
Suppose I have a 4-dimensional array -- in this case, of shape (3, 2, 2, 2):
a =...
- 1,365
0
votes
1
answer
76
views
Numpy: Move values according to another array
I've tried searching for it for a few hours now, but couldn't find a solution, so I hope someome can help me.
Assuming I have two numpy arrays that look like this:
data_arr = [[0 1 2]
[1 0 ...
- 11
1
vote
2
answers
155
views
Error in cv2.rectangle after flipping image with slicing: 'Layout of the output array img is incompatible with cv::Mat'
I am using OpenCV to draw a rectangle on a binary image. My goal is to draw the rectangle on both the original image and its vertically flipped version. However, I encounter an issue when flipping the ...
- 51