# Questions tagged [numpy]

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

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### Finding the closest point to a list of points

I'm trying to find the closest point (Euclidean distance) from a user-inputted point to a list of 50,000 points that I have. Note that the list of points changes all the time. and the closest distance ...
16k views

### Sending a C++ array to Python/NumPy and back

I am going to send a C++ array to a Python function as NumPy array and get back another NumPy array. After consulting with NumPy documentation and some other threads and tweaking the code, the code is ...
1k views

### Backpropagation in simple Neural Network

I've been working on a simple neural network implemented in python. Currently, it seems to be learning, but unfortunately it doesn't seem to be learning effectively. The graph below shows the output ...
3k views

### Remove points in a straight line

I wrote this code to remove points that create a straight line when plotted. For instance, this has many points in a straight line: ...
586 views

### Remapping and interpolating 255x1024 array

I have a function that accepts a $255\times1024$ array and remaps it to another array in order to account for some hardware related distortion (lines that should be straight are curved by the lens). ...
6k views

### Finding a zero crossing in a matrix

I am trying create an algorithm for finding the zero crossing (check that the signs of all the entries around the entry of interest are not the same) in a two dimensional matrix, as part of ...
307 views

### Solve the phase state between two haplotype blocks using markov transition probabilities

I have spent about more than a year in python, but I come from biology background. I should say I have got some understanding of for-loop and nested-for-loop to workout the solution to the problem I ...
314 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 ...
28k 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 ...
80k views

### Fastest way to iterate over Numpy array

I wrote a function to calculate the gamma coefficient of a clustering. The bottleneck is the comparison of values from dist_withing to ...
10k views

### Processing an image to extract green-screen mask

I am using OpenCV to process an image, and in my code, I have to check / edit each pixel separately: ...
384 views

### Warhammer: How many of my attacks will succeed?

Me and a couple of mates sometimes play a game called Warhammer. When playing the game you have options of what each model attacks. This can lead to situations where you know if you shoot with 100% of ...
392 views

### MNIST Deep Neural Network in TensorFlow

I have been working on this code for a while and it gave me a lot of headaches before I got it to work. It basically tries to use the MNIST dataset to classify handwritten digits. I am not using the ...
4k 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 ...
1k views

### Plot timings for a range of inputs

When writing Code Review answers, it becomes often necessary to measure how long the modified code takes vs how long the OP's code takes. I needed a nice way to visualize this as a function of the ...
546 views

### Generating Julia set

So, I just wanted to post something on Rosetta Code, and I found this task of generating and plotting a Julia set: http://www.rosettacode.org/wiki/Julia_set. There was already one solution but it was ...
2k views

### Pretty printing of the numpy ndarrays

Following this idea for pretty printing of numpy ndarrays, I have developed a very primitive prototype: ...
477 views

### Plotting different parameterized polynoms

For a university assignment I had to plot different polynomial functions depending on one single parameter. That parameter gave the number of supporting points to interpolate a given function in the ...
8k views

### Possible optimizations for calculating squared euclidean distance

I need to do a few hundred million euclidean distance calculations every day in a Python project. Here is what I started out with: ...
505 views

### Racetrack plotter

My Racetrack is just that. A Racetrack. You can't race it (yet) because I had trouble with collision detection, but I wanted to share it anyway. It creates a base polygon by using ...
828 views

### Plotting polynomials roots

NOTE: See follow up to this question here I created a simple python script to plot quadratic, cubic and quartic polynomials with integer coefficients between -4 and 4. It uses numpy to find the roots ...
6k views

### Faster computation of barycentric coordinates for many points

I'm just starting to understand the Python syntax and I created a module that does what I wanted, but really slow. Here are the stats of cProfile, top 10 ordered by ...
736 views

### Numerics for a game theory calculation using expected utility

I am trying to replicate Bruce B. de Mesquita's (BDM) results on political game theory for prediction. Based on where actors stand on issues, their capabilities, salience, BDM's method attempts to ...
746 views

### Temperature Interpolation

I want to interpolate temperature in correlation with height. I have temperature data from stations with coordinates and height in this format: ...
1k views

174 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, ...
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 ...
25k views

### Efficient numpy cosine distance calculation

I want to calculate the nearest cosine neighbors of a vector using the rows of a matrix, and have been testing the performance of a few Python functions for doing this. ...
13k views

### K-Mean with Numpy

I have implemented the K-Mean clustering Algorithm in Numpy: ...