I found an excellent and short introductory tutorial pdf on principal components analysis (PCA). It provides a good overview of the following concepts in a particularly intuitive manner:
1) Mean Average
2) Standard Deviation
3) Variance
4) Co-Variance
5) Matrix transformations
6) Eigenvectors & EigenValues
7) Principal Component Analysis
Unfortunately I found the eigenvectors bit a bit heavy going. Luckily the wikipedia page […]
Read Full Post »
I program in Python, Javascript and Factor on a roughly daily basis. My experience is that I can write functions/methods quicker in Python and Javascript than I can in Factor, but that my Factor code ends up being of considerably higher quality. By higher quality I mean that it’s better factored and easier to pull […]
Read Full Post »
Over the last few years I’ve read a number of books on stock trading but despite this I never really felt compelled to risk any of my own money on the markets.
Then in October I discovered that spread betting offers a cheap way to test the water on a small budget. Spread betting on markets […]
Read Full Post »
Last night I switched to using the Disqus service for comments on this blog and I must say I’m pretty impressed so far.
The reason for the switch is that I’m just not staying on top of wordpress upgrades and tweaks and so ideally I’d like to replace my current setup with something much simpler, […]
Read Full Post »
I shave every day and recently I’ve gotten tired of pissing money away on expensive mach3 blades. After dabbling a bit with cheap disposables without much joy I hit the internet for some shaving advice. A bit of research threw up the ‘double edge’ safety razor option and I decided to give it a […]
Read Full Post »
A colleague in my team at work has a theory regarding the nature of the much-hyped Dan Kaminsky DNS attack (which he’ll be revealing at Black Hat this year). Take it away Rob…
Read Full Post »
Motivated by Tom Moertel’s ‘A coders guide to coffee’, I’ve been experimenting with roasting my own coffee on the cheap. Here’s my equipment bought to date:
- Bodum 5679 C-Mill Electric Coffee Grinder
- Rival popcorn popper (cost me a fiver from ebay).
- Aeropress brewer
- Digital oven Thermometer 100169 E19
N.B. I didn’t start off roasting: a […]
Read Full Post »
Uncovered an awesome ssh trick today. At work we use ssh extensively to run stuff on remote unix and windows servers, using SSH agents to handle batch job authentication. That’s all sweet because on unix you don’t need to install client software on each box, and you don’t need a root account - just copy […]
Read Full Post »
Dan Ehrenberg completes a second short post on garbage collection, expanding on his excellent ‘Quick intro to garbage collection‘ post. Although Dan’s focus is on research prior to implementing a better collector for the factor language, the lucid explanations and chatty style make this a must-read for anybody with a passing interest in language runtime […]
Read Full Post »
Is it just me or do whitebox unit tests really bog you down?
I do pretty much all my coding in a test-first stylee; it’s the only way to code if you’re snatching 20mins here and there for spare time projects. Much of the time these tests serve as scaffolding to keep me on the […]
Read Full Post »
Learning Maths suddenly got easier when Kalid entered the scene. Better Explained has a ‘A Visual, Intuitive Guide to Imaginary Numbers‘ that’s every bit as penny-droppingly fantastic as his guide to exponential functions and e.
Trigonometry is great, but complex numbers make ugly calculations simple (like calculating cosine(a+b) ). This is just a preview; later articles […]
Read Full Post »
Jeff Atwood’s blog is a good source for collected quotes. He’s at it again in his latest post: Are you a Doer or a Talker?:
In software, some developers take up residence on planet architecture.’
‘Working code attracts people who want to code. Design documents attract people who want to talk about coding.’
In my experience talkers gravitate […]
Read Full Post »
Stumbled on this intuitive explanation of ‘e’ via a reddit comment today. Absolute internet solid gold - this is the first time I’ve actually understood exponential functions rather than just plugging ‘e’ into a formula.
The rest of the better explained site looks promising too!
Read Full Post »
Last year I embarked on somwhat of a journey to find a better language for my home projects after getting a bit frustrated by python’s lack of blocks and general cruftyness. After a couple of months of trying various different things I settled on Gambit Scheme for my spare-time data indexing project. A minimal core […]
Read Full Post »
JQuery is a javascript library providing a browser API in the functional style. In particular it supplies a CSS style selector language which makes the code for manipulating DOM objects simple and terse.
Simon Willison does a great job of introducing the library and explaining why it’s so cool. For a taster, here’s jquery line which […]
Read Full Post »
This link showed up on programming-reddit today. I’ve been reading Tim Bray’s ongoing blog for quite a while, but this piece from 2003 predates my discovery of it. And that’s a big shame because it is quite simply the most brilliantly readable overview to the whole topic of ‘large scale search’ that I’ve ever come […]
Read Full Post »
Neil Bartlett (who used to work at Dresdner Kleinwort, my employer) dropped me a mail to mention that he’s started a London Haskell User Group, and that the inaugural meeting on 29th 23rd May will include a talk by none other than Simon Peyton Jones of GHC and Software Transactional Memory fame!
Definitely one for […]
Read Full Post »
I found this SQL Injection Cheat-Sheet today (thanks reddit!). A must-read for anybody writing (or hacking into) web applications with a database.
Read Full Post »
For the computer scientists in the room:
Google techtalks rock, and this one about recent advances in retrieval techniques was especially interesting to me.
In particular it includes a remarkable recent observation for the improvement of hash tables: Hash table loading and performance can be dramatically improved simply by using more than one hash algorithm in […]
Read Full Post »
Pascal Costanza nails the point of macros.
(and illustrates why lispers actually like lisp’s strange syntax so much)
Read Full Post »
