python Programming Glossary: numpy.dot
Why is matrix multiplication faster with numpy than with ctypes in Python? http://stackoverflow.com/questions/10442365/why-is-matrix-multiplication-faster-with-numpy-than-with-ctypes-in-python no surprises here. Numpy implementation using numpy.dot a b Interfacing with C using ctypes module in Python. This is..
How does perspective transformation work in PIL? http://stackoverflow.com/questions/14177744/how-does-perspective-transformation-work-in-pil matrix dtype numpy.float B numpy.array pb .reshape 8 res numpy.dot numpy.linalg.inv A.T A A.T B return numpy.array res .reshape..
calling dot products and linear algebra operations in Cython? http://stackoverflow.com/questions/16114100/calling-dot-products-and-linear-algebra-operations-in-cython from Cython. Functions like numpy.linalg.inv inversion numpy.dot dot product X.t transpose of matrix array . There's a large..
Simple implementation of N-Gram, tf-idf and Cosine similarity in Python http://stackoverflow.com/questions/2380394/simple-implementation-of-n-gram-tf-idf-and-cosine-similarity-in-python between vectors v and u. This is equal to u.v u v . return numpy.dot u v math.sqrt numpy.dot u u math.sqrt numpy.dot v v For ngrams.. This is equal to u.v u v . return numpy.dot u v math.sqrt numpy.dot u u math.sqrt numpy.dot v v For ngrams def ngrams sequence n.. v . return numpy.dot u v math.sqrt numpy.dot u u math.sqrt numpy.dot v v For ngrams def ngrams sequence n pad_left False pad_right..
Scipy sparse… arrays? http://stackoverflow.com/questions/2540059/scipy-sparse-arrays in Compressed Sparse Row format And the timings timeit numpy.dot x x 10000 loops best of 3 123 us per loop timeit x_dok x_dok.T.. can do the dot product directly on the sparse data timeit numpy.dot x_csr.data x_csr.data 10000 loops best of 3 62.9 us per loop..
Numpy interconversion between multidimensional and linear indexing http://stackoverflow.com/questions/3257619/numpy-interconversion-between-multidimensional-and-linear-indexing You can simply calculate the index of each bin box_indices numpy.dot ndims numpy.arange ndims binassign The scalar product simply..
Finding k-nearest neighbors for a given vector? http://stackoverflow.com/questions/5684370/finding-k-nearest-neighbors-for-a-given-vector for i in range len knn.xs temp x knn.xs i dist numpy.sqrt numpy.dot temp temp order.append dist i order.sort # first 'k' are the..
Benchmarking (python vs. c++ using BLAS) and (numpy) http://stackoverflow.com/questions/7596612/benchmarking-python-vs-c-using-blas-and-numpy 1. Numpy The code used looks like this tNumpy timeit.Timer numpy.dot m1 m2 import numpy from __main__ import m1 m2 rNumpy.append..
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