Questions tagged [numpy]
NumPy is the fundamental package for scientific computing with the programming language Python.
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questions
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1answer
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2
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find max value in islands defined by other vector
I have a vector of values vals, a same-dimension vector of frequencies freqs, and a set of frequency values ...
3
votes
1answer
37 views
Path of a particle in a non-uniform B field
I have completed my project which simulates the path of a particle trapped in a device known as a magnetic mirror. I would like your thoughts and improvements on my implementation.
Here is the code:
<...
0
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0answers
35 views
Solving a linear system with Gaussian Elimination
I decided to implement a solver for linear systems of equations based on the gaussian elimination and reduction to upper triangular form. The gaussian elimination is quite simple to implement but the ...
4
votes
1answer
65 views
Function to calculate the GC content variation in a sequence
I came across this BMC Genomics paper:
Analysis of intra-genomic GC content homogeneity within prokaryotes
And I implemented some Python functions to make this available as part of a personal project.
...
2
votes
2answers
85 views
How can I optimize this pairwise Euclidean distance search algorithm?
x and y are two-dimensional arrays with dimensions (AxN) and (BxN), i.e. they have the same number of columns.
I need to get a matrix of Euclidean distances between each pair of rows from x and y.
I ...
1
vote
1answer
67 views
using pandas and numpy to parse dirty .csv
I'm relatively new to Python have been writing for a few months now. I've started a Pandas Numpy project that starts with parsing large and somewhat sloppy formatted textfile, its not exactly csv but ...
2
votes
1answer
51 views
Generating a matrix with each row having normalized weights
I just asked this question over Stack Over Flow on how to improve my code and reposting it here as someone on Stack Overflow recommended this platform.
I have written two python functions and they are ...
3
votes
0answers
50 views
Implementation of a crypto formula in Python
I need to implement in Python the formula in the image. The set B is a set of real numbers \$-1 \le t \le 1\$. Also, \$\mathbb{F}_2\$ is a set with the elements 0 and 1. \$y_i\$ is the \$i\$-th ...
2
votes
1answer
116 views
Implementing histogram in python
I was trying to implement my own version of matplotlib's hist function and I came up with this:
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1
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0answers
64 views
Using arrays more effectively with numpy
I previously posted some code I've been working on and had a fantastic answer, but as I didn't post the full code I was then unable to bring it all together using the much faster numpy implementation, ...
2
votes
1answer
96 views
Calculating a function over a large array
I have written some code to determine an interpolation matrix over a grid of points. I originally wrote the code in matlab, where under the specified parameters it took just over 2 minutes. The ...
0
votes
1answer
117 views
line-circle intersection [closed]
I have this code that generates a random line and a random circle.
...
2
votes
0answers
73 views
Python loading image into memory (numpy arrays) from database bytes field fast
I am looking for feedback on the function below to load a png image stored as bytes from a MongoDB into numpy arrays.
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13
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5answers
2k views
Iterate through two arrays calculating a statistic from indexes of zeros
I write a function which takes as input 2 arrays of zeros and ones ~8000 elements per array. Input array size is variable, can have much higher number of elements. The density of ones is expected to ...
3
votes
1answer
59 views
Dynamically indexing numpy array
I want to create a function that takes a numpy array, an axis and an index of that axis and returns the array with the index on the specified axis fixed. What I thought is to create a string that ...
0
votes
0answers
43 views
Vectorized code to find the position and length of runs of 1s in a bit matrix
I'm trying to write something like an adjusted run-length encoding for row-wise bit matrices. Specifically I want to "collapse" runs of 1s into the number of 1s in that run while maintaining ...
2
votes
0answers
32 views
Vectorizing a working custom similarity function further using numpy
I am new to python, and even more new to vectorization. I have attempted to vectorize a custom similarity function that should return a matrix of pairwise similarities between each row in an input ...
2
votes
1answer
103 views
Applying Minimum Image Convention in Python
I am computing pairwise Euclidean distances for 3-D vectors representing particle positions in a periodic system. The minimum image convention is applied for each periodic boundary such that a ...
3
votes
0answers
42 views
Nearest neighbor search algorithm of quantization
I'm doing some research on Nearest Neighbor Search of quantization, where running speed is very important. As I've just started using Python, I wonder if the following code for multi-processes can be ...
0
votes
1answer
31 views
Slow calculating sum of individual cells of matrix
I have a 3-D array in numpy, of dimensions 3000 x 2000 x 8
I need to modify the cells of the array so that each cell will contain the sum of all cells above and left of it, inclusive the current cell.
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2
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0answers
42 views
Convolution layer using numpy in python
I'm trying to make a CNN in python using numpy. I have a finished product but it seems that it can be improved. On testing the convolutional layer is the biggest bottleneck
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2
votes
1answer
78 views
Efficient Comparison Of Two Images Using Numpy
I want to compare 2 images using numpy. This is what I have got so far.
One of the outputs should be a white image with black pixels where pixels are different.
I ...
4
votes
0answers
51 views
How to structure and write exchangable calculation models (in python3 modules)?
I do research and compare different numeric models to each other. Therefore, I want to easily switch out the numeric models in my simulations and evaluation code.
Some models work in cartesian ...
7
votes
1answer
413 views
Genetic algorithm to guess coefficient of a polynomial
I have tried to code a genetic algorithm to guess the coefficients of a degree 4 polynomial. The information initially provided is values of y = f(x) for different x using the original polynomial. I ...
1
vote
0answers
90 views
Computing the angle between two vectors (vectorized) for small angles and with few copies
I am implementing a function that computes the angle between two vectors when given two n-dimensional arrays and an axis along which to operate. I want to do this with as few copies as possible, and ...
4
votes
1answer
81 views
Dataframe transformation to numpy ndarray takes ages to complete
I would like to transform my dataframe into an array of fixed-sized chunks from each unique segment. Specifically, I would like to transform the ...
0
votes
1answer
38 views
Get a "train or test" slicing elegantly after splitting
I am learning numpy, pandas, and sklearn for machine learning now. My teacher gives me code like below, but I guess it is ugly. This code is for splitting the data into training set and testing set, ...
1
vote
1answer
25 views
Removing Loop from Numpy XOR
I have been playing around with numpy and matplotlib.
My little project was to create a scatter plot ranging from -1 to 1 on both X and Y, but where the shading is done with the XOR scheme.
The ...
3
votes
1answer
52 views
Using Numba works slower than not using it for my Python code
I thought this community is better place to ask my question so I ask here rather than at StackOverflow.
Recently, I learned that Numba can make Python function ...
1
vote
1answer
57 views
Python utility to clean noise from flat text files
I have created simple code in which it takes flat file (txt) and eliminate the noise and error and only return clean rows, i.e. return flat file with the data I am interested in. it works fine but ...
0
votes
0answers
28 views
3
votes
1answer
89 views
Selecting a quantity from a list
I want to implement a function take_upto_n(A, n)
such that for e.g.
...
-1
votes
1answer
68 views
Speed up calculation time of for loop in numpy [closed]
I am trying to calculate some values using numpy. Here is my code,
...
0
votes
1answer
145 views
Fill missing dates into array of np.datetime
Here is the problem:
Given an array of a non-continuous sequence of dates. Make it a
continuous sequence of dates, by filling in the missing dates.
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2
votes
2answers
116 views
Finding distance between vectors of matrices
So here is the problem:
Given 2D numpy arrays 'a' and 'b' of sizes n×m and k×m
respectively and one natural number 'p'. You need to find the
distance(Euclidean) of the rows of the matrices 'a' and ...
6
votes
3answers
1k views
Marking duplicate entries in a numpy array as True
So the problem is
Find the duplicate entries (2nd occurrence onwards) in the given numpy
array and mark them as True. First time occurrences should be False.
And my solution is:
...
0
votes
0answers
71 views
Finding the Euclidean distance between the vectors of matrix a, and vector b
Here is the problem,
Given a 2D numpy array 'a' of sizes n×m and a 1D numpy array 'b' of
size m. You need to find the distance(Euclidean) of the 'b' vector
from the rows of the 'a' matrix. Fill the ...
4
votes
2answers
115 views
Creating nxm index list of array a
Here is the problem:
Given a numpy array 'a' that contains n elements, denote by b the set
of its unique values in ascending order, denote by m the size of
array b. You need to create a numpy array ...
2
votes
1answer
22 views
Reducing running time of creating integration field in flow field algorithm (python)
The integration field needs to get recalculated every time the starting or goal coordinates change. I wanted to use the flow field algorithm for a problem that includes bigger mazes with changing ...
5
votes
3answers
145 views
11
votes
1answer
173 views
From Hummingbirds to Ornithopters: Simulating the Aerodynamics of Flapping Wings
Ptera Software
A Flapping Wing Aerodynamics Simulator Written in Python
Motivation
About a year ago, I became fascinated by how animals fly. As an aerospace engineering student, it surprised me that ...
3
votes
1answer
52 views
Generating multiple new arrays using numpy
Say I have the following two different states:
state1 = [0, 1, 0, 1, 1]
state2 = [1, 1, 0, 0, 1]
And I want to generate n number of new states by only changing the ...
2
votes
1answer
781 views
Efficient NumPy sliding window function
Here is a function for creating sliding windows from a 1D NumPy array:
...
3
votes
0answers
35 views
Generating basic Fractals
Trying to generate fractals image with given IFS equations. I have two classes:
Shape - Gives co-ordinate to form a shape.
Ifs -...
1
vote
0answers
38 views
Reimplemented R function(s) is surprisingly slow
I reimplemented the functions https://rdrr.io/cran/fclust/man/RI.F.html, https://rdrr.io/cran/fclust/man/ARI.F.html and https://rdrr.io/cran/fclust/man/JACCARD.F.html of the R package https://rdrr.io/...
0
votes
1answer
86 views
Fast bruth force numpy array combination
I want to extract combinations of numpy arrays in that way:
...
2
votes
1answer
65 views
Performance issue in python- network creation based on the Euclidean distance with nested for loops is too slow
I want to create a network in which the links are formed based on a similarity metric defined as the Euclidean distance between the nodes. The distance is calculated using socio-demographic features ...
1
vote
1answer
94 views
decreasing solver speed
How can I decrease the time complexity and increase efficiency, without writing a new algorithm. My solution solves the majority of puzzles in a fast time, but for some difficult ones it can take over ...
2
votes
2answers
97 views
Downloading COVID data and uploading graphs
So this is a project I have been working on for the last few weeks. Just started learning Python. Started out with bash scripting and got the itch to learn more. Anyway code fetches covid-19 data from ...
