Random notes…
Product management · AI · Web3 · Real estate · Angel investments
-
Measuring user retention using cohort analysis with R
Cohort analysis is super important if you want to know if your service is in fact a leaky bucket despite nice growth of absolute numbers. There’s a good write up on that subject “Cohorts, Retention, Churn, ARPU” by Matt Johnson. So how to do it using R and how to visualize it. Inspired by examples…
-
Book review: Programming Amazon EC2
Should you buy a book on a new technology or just read technology provider’s guidelines, instructions and recommendations? This book was released over a year ago, so naturally it doesn’t cover all the latest developments that happened on Amazon AWS platform. For example Simple Email Service (SES) and Dynamo DB are not mentioned at all. After…
-
Heat map visualization of sick day trends in Finland with R, ggplot2 and Google Correlate
Inspired by Margintale’s post “ggplot2 Time Series Heatmaps” and Google Flu Trends I decided to use a heat map to visualize sick days logged by HeiaHeia.com Finnish users. I got the data from our database, filtering results by country (Finnish users only) in a tab separated form with the first line as the header. Three columns…
-
Setting up and securing web server (+MySQL +Rails/PHP) on Ubuntu 10.04 LTS
After repeating these operations many times in various setups, I decided to create a public set of instructions and share them with the world. This should be suitable for most of the simple web sites, utilizing Ruby on Rails or PHP. The setup works on Ubuntu 10.04 Server LTS (scheduled end of life April 2015). Other…
-
Book review: European Founders At Work
A book by Pedro Santos follows the format of Jessica Livingstone’s “Founders at Work”, offering a series of interviews with the founders of European start-ups. Entrepreneurs, such as Illya Segalovich (co-founder of Yandex), Loic LeMeur (founder of Seesmic and LeWeb), Peter Arvai (co-founder of Prezi) and many others (see full list on the book’s website: www.europeanfoundersatwork.com) tell about how they…
-
Informal notes from Strata 2012 conference on Big Data and Data Science
It’s been almost a month since I came back from California, and I just got around to sorting the notes from O’Reilly Strata conference. Spending time in the Valley is always inspiring – lots of interesting people, old friends, new contacts, new start-ups – it is the center of IT universe. Spending 3 days with…
-
Book review: The start-up of you
I bought this book because it was written by Reid Hoffman, co-founder of LinkedIn, and because it’s so damn easy to buy books on Kindle. It was a quick read, and I should say I’m a bit disappointed. If you want to save time and money – go to the book’s web page and you’ll get…
-
Book review: The Information Diet: A Case for Conscious Consumption
I read “Information Diet” by Clay Johnson last Christmas. Central ideas of the book: – information is like food – bad consumption habits are bad for your health – it’s too easy to get yourself into information bubble: “When we tell ourselves, and listen to, only what we want to hear, we can end up…
-
REE segfaults when Rails application has too many localisation files
We ran into an interesting problem – at some point of time our Rails application started to fail occaionally because of REE segfaults on startup. Even starting the console with ‘script/console production’ was occasionally failing with REE segfault. Application was growing, new features were added and segfaults started happening more and more often. There was…
-
Pitfalls of Rails fragment caching with memcached
Fragment caching is a powerful technique for improving performance of your web application. Rails site describes in detail how to apply this technique. Rails are providing developers with really excellent abstractions, but it’s always good to know what’s under the hood and how it all works. There are a few things that might potentially cause…