Topics › Mathematics

Finding the angle around an ellipse

When is the angle around an ellipse, not the around around the an ellipse? This is a problem which tripped me up a few times when working with elliptical orbits and arcs.

The problem

The issue is that we can (and often do) define the point on an ellipse at an angle, θ, with

x = a.cos(θ)
y = b.sin(θ)


Spinning globe

This post describes my highly convoluted method of making an animated globe using Khan Academy's computer science framework.

A few weeks ago I found a set of coordinates for a world map in JSON format. I can't remember where exactly, but I think it was via a StackOverflow question. The first thing I did was to convert it into an SVG world map, because I like SVG and I've been meaning to get a world map for a while.

Crude matrix multiplier

[Update: A slightly more sophisticated Javascript version of my program is available to use here]

Python regression finder

I've been working my way through Stanford's online Machine Learning course recently and I thought I should put some of what I've learnt to use.

The program I made (file below) reads a file of tab-delimited data, assuming the first column is the independent values (x) and the second is the dependent values (y). It then gives some options:


Salman says

Analysis of subtitle text from over 1000 Khan Academy videos. 

Python Fibonacci generator using reduce()

Khan Academy now has a series of videos on Python programming, and I've spent way too much of this weekend watching them, despite knowing all the basics of Python (I did learn a couple of things though). In fact, I spent so much time watching video, I finally broke the million point mark (and now have 77 points in binary):

My million points on Khan

Khan Academy

A few months ago, I wrote about various places to learn online, including the Khan Academy. Then a couple of weeks ago I saw a TED talk by Salman Khan where he talked about the Khan Academy (what else?) and its recent improvements. So I went back to the website and signed up.