Popular recipes tagged "numpy" but not "kinect"

Saving a numpy array to png image using fitz / MuPDF (PyMuPDF) (Python)

2016-03-19T12:57:38-07:00

Python recipe 580630 by Harald Lieder (fitz, image, mupdf, numpy, png, pymupdf). Revision 2.

If a pixel array is defined in numpy, it can be saved as a PNG image VERY fast if you use PyMuPDF.

Monte Carlo Engine : Stochastic Interest Rate Predictor (Python)

2014-04-27T16:42:29-07:00

Python recipe 578867 by alexander baker (carlo, interest, model, monte, numpy, rate). Revision 2.

This is a simple Monte Carlo Engine model, based on some ideas from the Quantopian folks. The idea is that the model and the engine are separate. I have integrated a simple example from an earlier post. The idea was to try and build some game theory simulations using simple models that were separate from the Engine.

Hartree Fock SCF (Python)

2013-04-30T09:09:20-07:00

Python recipe 578515 by alexander baker (numpy, physics). Revision 4.

Quantum Chemistry technique to calculate various interesting operators for HeH.

Locate and see the biggest cross in a random matrix (Python)

2013-09-13T13:31:03-07:00

Python recipe 578657 by alexander baker (numpy, python, search).

Interesting search space problem.

Conway's Game of Life In Python (Python)

2013-06-13T15:33:41-07:00

Python recipe 578559 by alexander baker (game, life, numpy, of, python, windows).

Conway's Game of Life In Python

How to read millions of hexadecimal numbers into a numpy array quickly (Python)

2012-06-27T06:03:40-07:00

Python recipe 578177 by Oren Tirosh (numpy).

The numpy.fromfile() function supports binary formats or decimal text. How do you read millions of hexadecimal numbers quickly?

Coordinates of numpy array from index and shape (Python)

2012-10-23T19:51:55-07:00

Python recipe 578302 by Garrett (convert, coordinates, index, numpy, python).

returns the coordinates of a numpy array given the index and the shape. A first_index_et function is given as example code

Fast Indexing functions (greater than, less than, equal to, and not equal to) (Python)

2012-03-13T16:21:36-07:00

Python recipe 578071 by Garrett (index, list, list_comprehension, numpy, python). Revision 2.

Oftentimes you want to find the index of a list-like object. Numpy arrays, for example, do not have a index member function. These get the job done quickly.

Note: these do not raise exceptions, instead they return -1 on error. You should change that if you want different behavior.

Fast Sorting of n dimensional array by first dimension (Python)

2012-03-14T15:14:11-07:00

Python recipe 578074 by Garrett (argsort, lists, numpy, python, sorting).

I have looked far and wide for code for fast sorting of n dimensional arrays by the first element, for example if I had the array:
ray = [[1,2,3,7,5][10,11,12,13,14]]

I would want it to come out as ray = [[1,2,3,5,7][10,11,12,14,13]]

There are several ways to do this. One is zipped = zip(ray) zipped.sort() ray = zip(zipped)

but this is extremely slow. Numpy has a much faster way to do it, but it wasn't immediately apparent.

if the above were a numpy array you could simply do the following: indexes = numpy.argsort(ray[0]) for n in xrange(len(ray)) ray[n] = ray[n][indexes]

I did a time test of the two methods below.

Conversion of PIL Image and numpy array (Python)

2011-03-05T03:47:56-08:00

Python recipe 577591 by Shao-chuan Wang (numpy, pil). Revision 2.

The utility function that converts PIL image to numpy array and vice versa.

Fastest way to list all primes below N in python (Python)

2010-07-27T01:57:20-07:00

Python recipe 577331 by robert.william.hanks (fast, fastest, math, numbers, numpy, primes, python). Revision 6.

I was looking for a fast way to list all primes below n, so far i came up to this with the numpy solution the fastest. It does primes up to 10e6 in 15ms in my old machine, and it is capable of reaching 10e9.

A fast & memory-wise prime number generator up to N (Python)

2010-08-13T18:28:00-07:00

Python recipe 577357 by robert.william.hanks (fast, numpy, primes, prime_generator, prime_number, python).

Using python 2.6 & numpy. This code was first posted here

Incremental PCA (Python)

2010-05-01T18:04:39-07:00

Python recipe 577213 by Micha Kalfon (incremental, klt, learning, numpy, pca, scipy, svd, vision).

An incremental PCA algorithm in python.

Incremental PCA allows computing an approximation of the principal components on large data sets as observations are given sequentially.

Infix operators for numpy arrays (Python)

2010-06-07T05:57:07-07:00

Python recipe 577201 by John Schulman (array, infix, matrix, multiplication, numpy). Revision 3.

This recipe adapts the infix operator trick from http://code.activestate.com/recipes/384122-infix-operators/ to give the appropriate behavior with numpy arrays, so you can write A *dot* B for np.dot(A,B)

UPDATE A solution to the dot problem was recently added to the numpy trunk: the dot method was added to the ndarray class so you can write a.dot(b). See http://projects.scipy.org/numpy/ticket/1456

Calculations on huge (memmap-)arrays (Python)

2009-05-05T10:19:37-07:00

Python recipe 576739 by d.schlabing (memmap, numpy, oop). Revision 2.

This is a way of doing calculations on whole arrays that might be to big to fit into memory.

Poor man's mgrid (Python)

2009-01-21T15:37:13-08:00

Python recipe 576625 by David Lambert (index, index_tricks, method, mgrid, numerical, numerical_methods, numpy, scipy, trick).

Python 3 code. scipy.mgrid is a useful! This short implementation comes without installing numpy.

pauli spin matricies (Python)

2008-08-26T01:52:06-07:00

Python recipe 576458 by alexander baker (kron, ladder, numpy, pauli, physics, spin).

simple spin investigation in python