NumPy is the fundamental package for scientific computing with the programming language Python.
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1answer
29 views
Counts instances for each category for many Matlab files
This is for machine learning. I have 5 matlab files: AWA, REM, S1, S2, SWS.
Each one has 2 arrays: x and y. ...
2
votes
1answer
53 views
Generate a random discrete signal
I currently have this code to generate a discrete signal with random amplitudes, but a fixed frequency:
...
8
votes
1answer
85 views
Monty Hall Optimization in Python 3.5
This is for homework but the deadline is over and I know the implementation is correct because it concurs with the math. At this point I just want to check my implementation for potential ...
4
votes
1answer
29 views
Surface Density Profile
I am trying to compute the surface density profile, given the spherical density profile in 3D for different parameters in order to interpolate and have it as a function of them to use later on for ...
4
votes
1answer
61 views
Conditional removal of columns in sparse matrix
I have a large dataset (78k instances x 490k features) that is loaded as a scipy.sparse.csr_matrix format. From this dataset I want to filter certain features (i.e. ...
5
votes
0answers
72 views
Two versions of Sudoku
I have written two versions of a sudoku solver. Both can solve 9x9 sudoku boards in <200 ms. One of the implementations uses numpy. I am looking for feedback on both, but particularly on why my ...
3
votes
2answers
40 views
Returning a NumPy array (or list) of strings of words repeated N times
I have a list of \$n\$ words, and a corresponding \$m \space x \space n\$ frequency matrix (as a NumPy array). I would like to return a list/array of strings of length \$m\$ where the \$m\$th string ...
4
votes
2answers
67 views
Export data from Python to spreadsheet
I have written the following code to export to data to a spreadsheet with this result:
Please let me know how to improve it.
...
1
vote
1answer
37 views
Mean of combined sublists with different lengths
I have a seemingly simple issue. Consider this list:
a = [[12.0, 5.0, 63.0], [0.1, 2.0, 7.1, 3.0, 2.3, 5.0, 8.4]]
I want to find the mean (using ...
5
votes
0answers
71 views
Computing intersections of a Polyline and a line
I wrote a script to compute / interpolate the nodes of a Polyline at a given latitude, input_lat. It works for my purpose but I am wondering if there is a better, ...
1
vote
1answer
78 views
Sum over selected numpy.ndarray column and write to a file
I am trying to write the sum of selected NumPy array column and write to a file.
The following code snippet is working fine:
...
6
votes
2answers
380 views
Crop black border of image using NumPy
Objective: Crop the image so only the number stays in the image
Problem: Slow Performance
I have code that crops an image.
The image pixels are 0 or 255. There are no values between.
The ...
2
votes
2answers
426 views
Plot heat map from csv file using numpy and matplotlib
There's a csv file with format:
x0, y0, v00
x0, y1, v01
...
x1, y0 v10
...
And what I want to do is to plot a heat map, in which at location (x, y) the value v ...
3
votes
1answer
57 views
Scoreboard with score evolution plots using classes
I've very recently started using OOP paradigms for the code in my work (academic research). As an exercise I tried coding this quick scoreboard.
I'm not interested in improving the 'display' part, I ...
4
votes
0answers
118 views
Optimizing the calculation of complex exponential numbers using OpenMP
I am trying to create a function that can either beat numexpr or perform comparably for the vectorized mathematical operation ...
3
votes
2answers
95 views
Assembling edges of a graph
I'm making a neural network that comprises five populations of feature-selective neurons and one population of non-selective neurons. Each neuron in this network receives connections from
c * f * ...
7
votes
2answers
165 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 e'...
5
votes
1answer
147 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
61 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
208 views
k-means clustering algorithm implementation
Here is my personal implementation of the clustering k-means algorithm.
...
2
votes
1answer
194 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
71 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
50 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 ...
3
votes
1answer
101 views
2
votes
0answers
30 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
53 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
80 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
20 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
200 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
vote
0answers
72 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
169 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
65 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
56 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
votes
0answers
67 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
83 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 ...
3
votes
2answers
54 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 off-...
2
votes
1answer
40 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 it'...
11
votes
3answers
169 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 links...
1
vote
3answers
569 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
360 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
60 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
90 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
414 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
2answers
166 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
84 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
117 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
57 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
125 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
24 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
133 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 ...
