Blog Archives

Movie Recommendations and More via MapReduce and Scalding

February 8, 2012
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Movie Recommendations and More via MapReduce and Scalding

Scalding is an in-house MapReduce framework that Twitter recently open-sourced. Like Pig, it provides an abstraction on top of MapReduce that makes it easy to write big data jobs in a syntax that’s simple and concise. Unlike Pig, Scalding is written in pure Scala – which means all the power of Scala and the JVM is already built-in....

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Quick Introduction to ggplot2

January 17, 2012
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Quick Introduction to ggplot2

For a much better looking version of this post (where code is actually readable!), see this Github repository, which also contains some of the example datasets I use and a literate programming version of this tutorial. Introduction This is a bare-bones introduction to ggplot2, a visualization package in R. It assumes no knowledge of R

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Quick Introduction to ggplot2

January 16, 2012
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Quick Introduction to ggplot2

This is a bare-bones introduction to ggplot2, a visualization package in R. It assumes no knowledge of R. For a better-looking version of this post, see this Github repository, which also contains some of the example datasets I use and a literate programming version of this tutorial. Preview Let’s start with a...

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Introduction to Conditional Random Fields

January 2, 2012
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Introduction to Conditional Random Fields

Imagine you have a sequence of snapshots from a day in Justin Bieber’s life, and you want to label each image with the activity it represents (eating, sleeping, driving, etc.). How can you do this? One way is to ignore the sequential nature of the snapshots, and build a per-image classifier. For example, given a month’s worth of...

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Winning the Netflix Prize: A Summary

October 23, 2011
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Winning the Netflix Prize: A Summary

How was the Netflix Prize won? I went through a lot of the Netflix Prize papers a couple years ago, so I’ll try to give an overview of the techniques that went into the winning solution here. Normalization of Global Effects Suppose Alice rates Inception 4 stars. We can think of this rating as composed of...

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Stuff Harvard People Like

September 28, 2011
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What types of students go to which schools? There are, of course, the classic stereotypes: MIT has the hacker engineers. Stanford has the laid-back, social folks. Harvard has the prestigious leaders of the world. Berkeley has the activist hippies. Caltech has the hardcore science nerds. But how well do these perceptions match reality?...

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Information Transmission in a Social Network: Dissecting the Spread of a Quora Post

September 7, 2011
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Information Transmission in a Social Network: Dissecting the Spread of a Quora Post

tl;dr See this movie visualization for a case study on how a post propagates through Quora. How does information spread through a network? Much of Quora’s appeal, after all, lies in its social graph — and when you’ve got a network of users, all broadcasting their activities to their neighbors, information can cascade in multiple

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Information Transmission in a Social Network: Dissecting the Spread of a Quora Post

September 6, 2011
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Information Transmission in a Social Network: Dissecting the Spread of a Quora Post

tl;dr See this movie visualization for a case study on how a post propagates through Quora. How does information spread through a network? Much of Quora’s appeal, after all, lies in its social graph – and when you’ve got a network of users, all broadcasting their activities to their neighbors, information can cascade in multiple ways. How...

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Introduction to Latent Dirichlet Allocation

August 21, 2011
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Introduction to Latent Dirichlet Allocation

Introduction Suppose you have the following set of sentences: I like to eat broccoli and bananas. I ate a banana and spinach smoothie for breakfast. Chinchillas and kittens are cute. My sister adopted a kitten yesterday. Look at this cute hamster munching on a piece of broccoli. What is latent Dirichlet allocation?...

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Tweets vs. Likes: What gets shared on Twitter vs. Facebook?

July 28, 2011
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Tweets vs. Likes: What gets shared on Twitter vs. Facebook?

It always strikes me as curious that some posts get a lot of love on Twitter, while others get many more shares on Facebook: What accounts for this difference? Some of it is surely site-dependent: maybe one blogger has a Facebook page but not a Twitter account, while another has these roles reversed. But even

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