# Questions tagged [numpy]

NumPy is the fundamental package for scientific computing with the programming language Python.

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40 views

### Calculate of the average of time discounted values

Given the current table: ...
23 views

### 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 ...
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: <...
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 ...
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. ...
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 ...
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 ...
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 ...
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 ...
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: ...
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, ...
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 ...
117 views

### line-circle intersection [closed]

I have this code that generates a random line and a random circle. ...
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. ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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. ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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, ...
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 ...
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 ...
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 ...
28 views

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### Selecting a quantity from a list

I want to implement a function take_upto_n(A, n) such that for e.g. ...
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, ...
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. ...
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 ...
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: ...
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 ...
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 ...
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 ...
145 views

### Optimizing an implementation of the RKF method

This is an algorithm regarding the RKF method: ...
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 ...
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 ...
781 views

### Efficient NumPy sliding window function

Here is a function for creating sliding windows from a 1D NumPy array: ...
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 -...
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/...
86 views

### Fast bruth force numpy array combination

I want to extract combinations of numpy arrays in that way: ...
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 ...