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

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6
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1answer
45 views

Histogram of a string

I'm teaching myself Python and when a friend posted this sentence Only the fool would take trouble to verify that his sentence was composed of ten a's, three b's, four c's, four d's, forty-six ...
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0answers
37 views

Iterating through a list of lists of tuples [on hold]

I have this function neighbor that works on this matrix: ...
5
votes
1answer
79 views

Koch snowflake in Python with numpy and pygame

I've drawn a Koch snowflake with Python 3. I'm new to the Python world and would appreciate all feedback on how to make the code more Pythonic as I'm not used to these idioms, styles and modules. All ...
3
votes
1answer
45 views

Normalizing data over a distribution

I have a list X containg the data performed by different users N so the the number of the ...
5
votes
1answer
79 views

k-means clustering algorithm implementation

Here is my personal implementation of the clustering k-means algorithm. ...
2
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1answer
58 views

Check if a numpy array contains numerical data

This function serves me as a testing-utility to check if the result is really numeric and sometimes as input-validation if there are a lot of operations before I would find out (with an Exception) if ...
1
vote
1answer
39 views

Finding cointegrated pair with minimal t-score

The function findMinimal() receives a tuple from a list which contains 171 tuples, each of them go into the function one by one and, for each tuple, it searches the ...
3
votes
1answer
37 views

Slicing a big NumPy array

I have a function that takes a four-dimensional NumPy array M and, for each value i of its second index, takes all of M without the i-th "column", evaluates the product over all other columns, and ...
1
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0answers
43 views

Checking convergence of 2-layer neural network in python

I am working with the following code: ...
2
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0answers
28 views

Picking seats in a matrix

I'm trying to write a Python class that creates a matrix of zeros, then uses a random number generator to pick 'seats' on the matrix. It changes the zero in that seat to a one, until the matrix is all ...
2
votes
1answer
48 views

Performance optimization when switching from nested to flat representation (genetic algorithm)

The code below is the core of a Genetic Algorithm (NSGA-II to be precise, without crowding-distance calculation), but I've taken out all the GA-specific parts and made a generic example. I think I've ...
2
votes
1answer
70 views

Project Euler problem #11 - Largest product in a grid

I have recently solved the following Project Euler problem: In the 20×20 grid below, four numbers along a diagonal line have been marked in red [here bold]. ...
1
vote
1answer
10 views

Organizing a Python list of lists as function of number of occurances

I am having a Python list of lists, that I get as an output of python-igraph (membership to clusters). The integers represent an association of a vertex to a ...
5
votes
1answer
80 views

Python Octree Implementation

I'm working with 3D point clouds stored in Numpy arrays. I'd succesfully used the scipy's KDTree implementation for task like k-neighbors search and outlier filtering. However I wanted to try the ...
1
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0answers
40 views

Snell's law using Zoeppritz equation by matrices

I have created the following code to calculate Snell's law angles, based on Zoeppritz equations on complex plane. The code works, seems it is returning valid values, but after all the code just looks ...
2
votes
2answers
105 views

Simulation of 2D elastic balls

Following this SO post and this Wikipedia article, I wrote a Python script to simulate physics of 2D elastic balls. I define the physical behaviour of each ball in the ...
0
votes
1answer
57 views

Computing logits for a vector and for all vectors in a set

I've had to write two different functions (shown below), but I want to combine the two functions into one. Is there a way to do this? softmax_a_set() takes a list ...
2
votes
1answer
39 views

Quickly find percentile with high precision

I need to find the percentile where a list of values is higher than a threshold. I am doing this in the context of optimization, so it important that the answer is precise. I am also trying to ...
0
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0answers
57 views

Memory efficient alternative passing mostly static variables w/ 1 dynamic variable to an external function (COM) instead of a for loop in Python

Massive data problem, 7/8 variables are repeated 1000 times in a for loop, sending 8 input vectors * 50,000 values per loop for each function call. Only 1 input ...
1
vote
1answer
47 views

Finding the percentile corresponding to a threshold

I need to find which percentile of a group of numbers is over a threshold value. Is there a way that this can be speed up? My implementation is much too slow for the intended application. In case this ...
2
votes
1answer
27 views

In matrix of sub-matrices, select diagonal indices of off-diagonal submatrices

Let's say I have a square matrix of size (n*m) x (n*m) that is composed of n x n sub-matrices, with each submatrix being a square of size m x m. I want to select the diagonal indices of the ...
2
votes
1answer
35 views

Measuring the distance between NumPy matrixes

This takes two sets of five random points stored as a NumPy matrix, and then calculates the NumPy matrix between a point of the first set and a point of the second set. While the code works, I feel ...
11
votes
3answers
143 views

Fast Python spring network solver

I wanted a very simple spring system written in Python. The system would be defined as a simple network of knots, linked by ...
1
vote
3answers
204 views

Recursively Save Python Dictionaries to HDF5 Files Using h5py

I have a bunch of custom classes for which I've implemented a method of saving files in HDF5 format using the h5py module. A bit of background: I've accomplished ...
9
votes
1answer
139 views

Simple Phase Locked Loop

Here is a simple Phase Locked Loop, which is a circuit used in radio communications for synchronisation between transmitter and receiver. The loop works by calculating the (phase) difference between ...
2
votes
1answer
54 views

Sampling with weighted probabilities

In an exam question I need to output some numbers self.random_nums with a certain probability self.probabilities: I have ...
3
votes
3answers
77 views

Creating and manipulating FITS files

I wrote a program that manipulated data from VLA observations and created FITS files to be used in creating spectral energy distributions of high redshift radio galaxies. I really tried to be as ...
2
votes
2answers
180 views

Efficiently index rows of numpy array by exclusion

I need a function that takes a numpy array and a row number as inputs and returns the array (or copy of the array) excluding the given row. I want to do this as efficiently as possible. ...
4
votes
1answer
88 views

Skip list in Python

I've made an attempt at writing a skip list in Python. I'm using NumPy to generate geometric random variables, but since that's a bit of a heavy dependency to drag around I could easily implement that ...
3
votes
1answer
45 views

Comparing pixels against RGB value in NumPy

Assume I created an image in NumPy: image = imread(...) And the image is RGB: ...
5
votes
2answers
103 views

Attempting to run multiple simulations of the Gillespie algorithm for a set of stochastic chemical reactions in less than 10 minutes

I have written Python code that generates a plot. In the code below, when I set maxtime = 0.1, the program takes ~50s and when I set ...
1
vote
1answer
46 views

Write binary save file in Python

I'm fixed on the save file format. There are only three types of data: long (NumPy int32 array, independent of platform) ...
5
votes
2answers
119 views

Jacobian product

Do you have in mind a way to compute the following sum $$R_{i,j,k} = \sum_{l=0}^{2} J_{i,j,l+3k} v_{i,j,l}$$ obviously in a vectorised fashion? This may sound like an equivalent of: ...
1
vote
0answers
22 views

Spatial parametric scaling in agent-based model

I’m running a simple agent-based disease spread model on a 2D lattice, where disease transmission in a population depends on each individual’s chance of avoiding infection at every time step, which ...
4
votes
2answers
120 views

Backtracing Sudoku solver

I have made a backtracking Sudoku solver in Python but it's working quite slow. Originally, It had been working on 4 by 4 grids, which worked fine. But now, trying to solve 9 by 9 grids takes a very ...
8
votes
2answers
60 views

Iterate list to map entries in Python

I have two files, namely: File1: CL1 AA XX YY ZZ SS \n CL2 3_b AA File2: AA string1 AA string2 3_b string3 My ...
9
votes
2answers
100 views

A 3-D vector class built on top of numpy.array

I wanted a convenient class to easy access the parameters inside. I am using a lot of math in my game; that's why a wanted to access them through x, ...
7
votes
1answer
102 views

Optimizing a python script with large arrays

I have a python script that I'd like to speed up. I'm hoping some of the gurus here can offer some advice. The script reads in some data from file: 2 arrays with lat/lon vals, 3 arrays with image ...
6
votes
1answer
187 views

Combining two clock tick vectors with NumPy

I have two long (7683200 length) 1D arrays corresponding to two clock cycles, that I wish to combine into single 1D array. The clock_ticks_fine cycles between ...
14
votes
3answers
366 views

Orbital Trajectory simulator

I have written a simple program to do trajectory simulation in the Earth-Moon system, it still has a long way to go I am working on making it more class oriented and am looking into implementing a ...
5
votes
1answer
167 views

A matplotlib scatter function inside a for loop

This function is working exactly as I want, only, it's taking too long. For speed ups, I've tried to do as much as I can before the main for loop by declaring ...
0
votes
1answer
104 views

Benchmark using floating point math

I wrote some code in Python, to benchmark mathematical operations. It does not do anything in particular besides just calculating a lot of floating point numbers. To clarify: I need 128-bits ...
6
votes
3answers
96 views

Python differential analysis of heat loss across a pipe

I made a differential equation solver to forecast heat loss through a pipe with heat loss coefficient contours. It does what I want it to do but I had to use global variables to change the outputs of ...
2
votes
1answer
180 views

Cross validation of gradient boosting machines

I am fairly new to Python. I implemented a short cross-validation tool for gradient boosting methods. ...
3
votes
1answer
348 views

“back substitution” method for solving linear system

I'm using numpy to write the "back substitution" method for solving linear system where "A" is a nonsingular upper triangular matrix. ...
1
vote
1answer
89 views

Latent Dirichlet Allocation in Python

I've recently finished writing a "simple-as-possible" LDA code in Python. The theory from which I've developed my code can be found in the book Computer Vision by Simon Prince, free (courtesy of ...
4
votes
1answer
161 views

Applying a formula to 2D numpy arrays row-wise

The user has two 2D input arrays A and B, and a given matrix S. He wants to apply a ...
2
votes
1answer
43 views

Extracting an arbitrary element from each row of a np.array

I have a large numpy array of shape (n,m). I need to extract one element from each row, and I have another array of shape (n,) that gives the column index of the element I need. The following code ...
3
votes
1answer
3k views

ID3 Decision Tree in python

I've been working my way through Pedro Domingos' machine learning course videos (although the course is not currently active). His first homework assignment starts with coding up a decision tree ...
1
vote
3answers
81 views

Convert scalar arguments to arrays, and check that lengths are equal

I've got a Python function that takes two arguments, lat and lon. These arguments can be either scalar values (...