Questions tagged [numpy]
NumPy is the fundamental package for scientific computing with the programming language Python.
95
questions with no upvoted or accepted answers
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votes
0answers
269 views
Efficiently selecting spatially distributed weighted points
Background:
Motivation behind writing the following code is originated in the area of computer vision. More specifically – image rectification. In order to obtain rectified images, one has to find a ...
10
votes
1answer
1k views
Parallelizing some model fitting code using multiprocessing
I'm trying to refactor some code for fitting parametric models that are defined symbolically using Theano. My goal is for all models to expose a common interface so that, as far as possible, they can ...
8
votes
0answers
160 views
Population dynamic simulation on biological information maintenance 2
This question is the follow-up to this previous question.
Background
Using this simulation I investigate a system in which enzymes proliferate in cells. During the replications of enzymes, ...
6
votes
0answers
54 views
Numerical integration in cython
I have a set of nested functions that I need to call multiple times. I know scipy.quad is pretty fast, but I will need to call the integrator recursively and want ...
6
votes
0answers
51 views
Find indices using for loop
I should estimate the effect of B fields on particle deflection using \$F=V \times B \times Force\$.
I have a 2D mesh with \$n_x\$ and \$n_y\$ which show the number of points in each direction. \$B\$ ...
6
votes
0answers
2k views
Calculating T-Test within Large Pandas Dataframes
The below code runs a t-statistic within a large dataframe (rnadf) based on masked values from another dataframe (cnvdf_maked). ...
6
votes
0answers
272 views
Summing 2D NumPy array by multiple labels
Each element of the array is a coordinate (x, y).
Each coordinate has two labels.
Goal:
sum the elements that have the same two labels.
How can ...
5
votes
0answers
62 views
Cubic spline interpolation in Python from scratch
I implemented the cubic spline interpolation explained in
https://en.wikipedia.org/wiki/Spline_interpolation as a Python class. Of course, such an interpolation should exist already in some Python ...
5
votes
0answers
83 views
Implementing numerical integration in Python
I have this Python code that implements a rectangular numerical integration. It evaluates the (K-1)-dimensional integral for arbitrary integer \$K \geq 1\$
$$\int_{u_K = 0}^{\gamma}\int_{u_{K-1} = 0}^...
5
votes
0answers
1k views
Plotting the Mandelbrot set at different zoom levels
I'm interested in making an animated movie of a zoom in on a part of the Mandelbrot set. My code works well for a few zooms, but upon trying to zoom in quite far, I find that the fractal becomes "...
5
votes
0answers
473 views
Calculating complex exponential numbers using OpenMP in Cython
I am trying to create a function that can either beat numexpr or perform comparably for the vectorized mathematical operation ...
4
votes
2answers
17 views
Grouping sorted coordinates based on proximity to each other
I created an algotrithm that groups a sorted list of coordinates into buckets based on their proximity (30) to one another.
Steps:
Create a new key with a list ...
4
votes
0answers
35 views
Evaluate joint probability density function of a Markov random field
The following code evaluates probability mass function for all possible states of a model.
...
4
votes
1answer
73 views
4
votes
0answers
213 views
Occupancy map creation using positions
This code basically check whether a person is in the grid of another person.
The algorithm should check all possible 2-permutations of persons whether a person is in another person grid. In the first ...
4
votes
0answers
392 views
numpy 2d array anti diagonal averaging
The following piece of code averages the ante-diagonal elements of a 2d array x of size (m,n) with, for my purpose, m > n.
...
4
votes
0answers
945 views
Pandas/Numpy statistical odds ratio test
I'm looking for a faster way to do odds ratio tests on a large dataset. I have about 1200 variables (see var_col) I want to test against each other for mutual exclusion/ co-occurrence. An odds ratio ...
4
votes
0answers
1k views
Applying hysteresis to a signal
Using python 3.6. I have written this code (below) to apply hysteresis to a signal (a numpy array).
My aim was to create a function that didn't require any loop to remember the previous state of the ...
4
votes
0answers
512 views
Color image classification and labeling algorithm
I have some code I've been using to de-noise some images and then label all unique and contiguous elements. The function zoneMap() de-noises the image by picking a ...
4
votes
0answers
201 views
Finding where column slices of elements in multi-dimensional array are equal
Skippable Intro:
I have a dataset that corresponds to an observed time-series. The dataset is organized into a dictionary - which contains an array of years, an array of months, an array of days, an ...
4
votes
0answers
2k views
Reducing memory consumption for Numpy array
I'm running the following code using numpy arrays, I get a MemoryError in Ubuntu, while the same code runs on Mac OSX. (Pagination is automatically setup in Mac) This process consumes around 30 GB. ...
4
votes
0answers
409 views
Find the closest parametric values corresponding to a BSpline's control points
On a curve generated by scipy.interpolate.BSpline I want to find the closest
parameters relative to each control point, so that the given parametric range is ...
4
votes
0answers
784 views
2-D Kalman Filtering in Python using Numpy
I am practicing Kalman filtering and wrote a short python class that uses Numpy to calculate the 2-D kalman filter for position and velocity along the X axis: assume that the object is only moving ...
4
votes
0answers
2k views
Implementation of the Householder Transformation
I implemented the Householder transformation in Python, so that I can later use it in a QR decomposition. Unfortunately I haven't found a good concise source for reading up on the algorithm.
I am not ...
4
votes
0answers
176 views
Simple Stateful LSTM example with arbitrary sequence length
I'm trying to make a simple example showing how to create a RNN with Keras that accepts as input a sequence of arbitrary length. In my example, the LSTM is trying to classify whether a sequence has ...
4
votes
0answers
459 views
Customizable Multi-Agent Predator/Prey Simulation
I am trying to create a highly customizable "battle simulator". The default setup is a predator/prey relationship (no births); however, I am trying to create code such that it's easy to add and ...
4
votes
0answers
327 views
Plant/Residue Detection project, How to structure it?
Introduction
I have wanted to develop this project for more than two years. I just started writing it a couple days ago. I use it to detect plant or residue pixels in crop row images but it provides ...
4
votes
0answers
379 views
Python Code For Drawing a Fractal Tree using pyglet
So I've just finished doing a coding challenge that involved drawing a fractal tree. Instead of doing it recursively(which is what I did initially but it proved to be to slow for branches greater than ...
4
votes
0answers
1k views
Implementing the stochastic gradient descent algorithm of the softmax regression with only NumPy
I am implementing the stochastic gradient descent algorithm. I think there is plenty of room for improvement.
...
4
votes
0answers
199 views
Generalized NumPy reshape function to imitate einsum syntax
I often perform a lot of reshape(), transpose() or squeeze() operations on ...
3
votes
0answers
32 views
Implementing a tic tac toe board in python
This is my attempt at making a class to represent a game board for tic tac toe. I normally hate while loops but I used one because I cant seem to make the ...
3
votes
0answers
54 views
Optimising Probabilistic Weighted Moving Average (PEWMA) df.iterrows loop in Pandas
I'm implementing the Probabilistic Exponentially Weighted Mean for real time prediction of sensor data in pandas but have issues with optimising the pandas notebook for quick iterations.
Is there a ...
3
votes
0answers
19 views
TensorFlow regressor to predict probability of winning, given a current score
This is a TensorFlow regressor that tells me that if you get x score, you will have x% to win a game in x game(game is not important).
Doing this as a project to learn tensorflow.
...
3
votes
0answers
33 views
N-D Kalman Filter in Python + Numpy
Just implemented this Kalman Filter in Python + Numpy keeping the Wikipedia notation
It's a pretty straightforward implementation of the original algorithm, the goals were
develop skills related to ...
3
votes
0answers
54 views
Locality Sensitive Hash (similar to k-Nearest Neighbor), in Python+Numpy
I've tried implementing Locality Sensitive Hash, the algorithm that helps recommendation engines, and powers apps like Shazzam that can identify songs you heard at restaurants.
LSH is supposed to run ...
3
votes
0answers
55 views
Computing Doppler delay on a meshgrid
Objective
Plot the contour of the iso-doppler and iso-delay lines for a transmitter-receiver reflection on a specular plane.
Implementation
This Doppler shift can be expressed as follows:
$$f_{D,0}(...
3
votes
0answers
59 views
Minimization problem solving and its step limits
I am trying to solve the following minimization problem:
$$
\min\lvert\lvert{x}\rvert\rvert_1 + \beta\lvert\lvert{x}\rvert\rvert^2_2 s.t. \sum_{m = 1}^M (y - \lvert{c}^{H} . x\rvert^2)^2 \le \epsilon
...
3
votes
0answers
671 views
Distance transform on image using NumPy
I would like to find the find the distance transform of a binary image in the fastest way possible without using the scipy function distance_transform_edt(). The ...
3
votes
0answers
64 views
Variable bit length lossy floating point compression
I am implementing a new compression algorithm for the weights of a neural network for the Leela Chess project. the weights are roughly 100Mb of ...
3
votes
0answers
63 views
Data set generation with Python and Matplotlib
I want to use Python and Matplotlib to create a data set of images. I want to do this by transforming the plot to a numpy matrix. At the moment it takes about 0.1 second to generate 100 images of size ...
3
votes
0answers
87 views
Searching for the location of a sub-image within an image
I have a number of images that were cropped and their backgrounds removed. I've tried to write a function that will search the original unmodified image for the cropped image so that I can restore the ...
3
votes
0answers
94 views
Merging bin-data via a bin count threshold
When performing a chi-squared test, one takes the square of the differences of the expected counts per bin and observed counts per bin, and divides these per-bin differences by the expected counts per ...
3
votes
0answers
56 views
Numpy versus Theano GPU parallelization
I am learning Theano to accelerate my image processing functions. As a start, I am trying to reimplement the function to turn images from colors to black and white (with the same number of channels): ...
3
votes
0answers
42 views
Deriving incremental feature representations for bit flips
Given a boolean 3D matrix and a set of actions specifying bit flips at certain positions, a set of resulting matrices can be obtained, one matrix for each action, as if executing each bit flip ...
3
votes
0answers
2k views
Reading a csv file and making a histogram in Python using NumPy and Matplotlib
I have written the following code which reads a csv file that contains a bunch of words and their sentiment value. Words like abandon may have a value of -1, while words like progress and freedom have ...
3
votes
0answers
224 views
Applying Scikit-Learn Linear Kernel with a generator for low memory pressure
matrix = # a sparse matrix of TFIDF vectors - 28458x3218988
My aim was to create a similarity matrix comparing all documents to all documents using ...
3
votes
0answers
420 views
pandas time-based qcut
I have a dataframe pairs where each row is a transaction with corresponding price and date. Now, I need to assign each transaction to a quintile (add a new column), ...
3
votes
0answers
114 views
Simple finite difference employing Maccormack technique
I am relatively new to programming and while I am fairly comfortable with the math, I cannot say with confidence that I feel the same way with programming. Anyway here is a simple finite difference ...
3
votes
0answers
131 views
Speed up a Gibbs sampler with Cython
I have implemented a Gibbs sampler to generate textured images. According to the beta parameters (array of shape(4)), we can generate various textures.
Here is my ...
3
votes
0answers
339 views
Cythonized version of FDCT (fast discrete cosine transform) function, ported from Java
This is my Cython code for an FDCT function (invoked here):
...
