Yes, this is clearly nonsense. Sorting is not a hard problem and standard algorithms such as quicksort and mergesort have O(x^2) and O(n log(n)) complexity. But let me scratch this itch of sorting numbers using an evolutionary algorithm, specifically Covariance matrix adaptation evolution strategy (CMA-ES). Technically, we will use what I think is the original …
How to sort numbers with an evolutionary algorithm (CMA-ES) Read More »
This article on causal machine learning covers a practical example of how to learn structural causal models (SCM) directly from data. We will use bnlearn, which is an open-source library for learning the graphical structure of Bayesian networks in Python. Check out my Github repo for additional code examples. For other frameworks, checkout my page …
Cosine similarity is the normalised dot product between two vectors. I guess it is called “cosine” similarity because the dot product is the product of Euclidean magnitudes of the two vectors and the cosine of the angle between them. If you want, read more about cosine similarity and dot products on Wikipedia. Here is how …
Step one: brew install glpk pip install pulpbrew install glpk pip install pulp Step two: from pulp import * prob = LpProblem("test1", LpMinimize) # Variables x = LpVariable("x", 0, 4, cat="Integer") y = LpVariable("y", -1, 1, cat="Integer") z = LpVariable("z", 0, cat="Integer") # Objective prob += x + 4*y + 9*z …
Whenever two things have a directional relationship to each other, then you can compute the pagerank of those things. For example, you can observe a directional relationships between web pages that link to each other, scientists that cite each other, and chess players that beat each other. The relationship is directional because it matters in …
Having reinstalled PostgreSQL with support for Python and pointing at my non-system python, it is time to test whether I can use the convex optimizer library I’ve installed in my Python 2.7 (pip install cvxopt). Install PL/Python if not already installed — if not already installed. Doesn’t hurt. CREATE extension plpythonu;– if not already installed. …
In a project I’m going to use clustering algorithms implemented in Python, such as k-means. Clustering http://stackoverflow.com/questions/1545606/python-k-means-algorithm scipy.cluster has been reported to have some problems, so for now I’ll use PyCluster (following advice given on stackoverflow). Install PyCluster: pip install PyClusterpip install PyCluster
Fast compression algorithms like Snappy, QuickLZ and LZ4 are designed for a general stream of bytes, and typically don’t treat byte-sequences representing numbers in any special way. Geospatial data is special in the sense that it often contains a large amount of numbers, like floats, representing coordinates.
Rtree is a ctypes Python wrapper of libspatialindex that provides a number of advanced spatial indexing features for the spatially curious Python user.
A friend of mine, who is the CEO of a company that develops an embedded database, asked me to do a presentation on spatial indexing. This was an opportunity for me to brush up on R-trees and similar datastructures. Download the slides The presentation introduces R-trees and spatial indexing to a technical audience, who are …