mathbabe

Our first speaker this week in Rachel Schutt‘s Columbia Data Science course was John Kelly from Morningside Analytics, who came to talk to us about network analysis.

John Kelly

Kelly has four diplomas from Columbia, starting with a BA in 1990 from Columbia College, followed by a Masters, MPhil and Ph.D. in Columbia’s school of Journalism. He explained that studying communications as a discipline can mean lots of things, but he was interested in network sociology and statistics in political science.

Kelly spent a couple of terms at Stanford learning survey design and game theory and other quanty stuff. He describes the Columbia program in communications as a pretty DIY set-up, where one could choose to focus on the role of communication in society, the impact of press, impact of information flow, or other things. Since he was interested in quantitative methods, he hunted them down, doing his master’s thesis work with Marc Smith from Microsoft. He worked on political discussions and how they evolve as networks (versus other kinds of discussions).

After college and before grad school, Kelly was an artist, using computers to do sound design. He spent 3 years as the Director of Digital Media here at Columbia School of the Arts.

Kelly taught himself perl and python when he spent a year in Viet Nam with his wife.

Kelly’s profile

Kelly spent quite a bit of time describing how he sees math, statistics, and computer science (including machine learning) as tools he needs to use and be good at in order to do what he really wants to do.

But for him the good stuff is all about domain expertise. He want to understand how people come together, and when they do, what is their impact on politics and public policy. His company Morningside Analytics has clients like think tanks and political organizations and want to know how social media affects and creates politics. In short, Kelly wants to understand society, and the math and stats allows him to do that.

Communication and presentations are how he makes money, so that’s important, and visualizations are integral to both domain expertise and communications, so he’s essentially a viz expert. As he points out, Morningside Analytics doesn’t get paid to just discover interesting stuff, but rather to help people use it.

Whereas a company such SocialFlow is venture funded, which means you can run a staff even if you don’t make money, Morningside is bootstrapped. It’s a different life, where we eat what we sow.

Case-attribute data vs. social network data

Kelly has a strong opinion about standard modeling through case-attribute data, which is what you normally see people feed to models with various “cases” (think people) who have various “attributes” (think age, or operating system, or search histories).

Maybe because it’s easy to store in databases or because it’s easy to collect this kind of data, there’s been a huge bias towards modeling with case-attribute data.

Kelly thinks it’s missing the point of the questions we are trying to answer nowadays. It started, he said, in the 1930’s with early market research, and it was soon being applied applied to marketing as well as politicals.

He named Paul Lazarsfeld and Elihu Katz as trailblazing sociologists who came here from Europe and developed the field of social network analysis. This is a theory based not only on individual people but also the relationships between them.

We could do something like this for the attributes of a data scientist, and we  might have an arrow point from math to stats if we think math “underlies” statistics in some way. Note the arrows don’t always mean the same thing, though, and when you specify a network model to test a theory it’s important you make the arrows well-defined.

To get an idea of why network analysis is superior to case-attribute data analysis, think about this. The federal government spends money to poll people in Afghanistan. The idea is to see what citizens want and think to determine what’s going to happen in the future. But, Kelly argues, what’ll happen there isn’t a function of what individuals think, it’s a question of who has the power and what they think.

Similarly, imagine going back in time and conducting a scientific poll of the citizenry of Europe in 1750 to determine the future politics. If you knew what you were doing you’d be looking at who’s marrying who among the royalty.

In some sense the current focus on case-attribute data is a problem of what’s “under the streetlamp” – people are used to doing it that way.

Kelly wants us to consider what he calls the micro/macro (i.e. individual versus systemic) divide: when it comes to buying stuff, or voting for a politician in a democracy, you have a formal mechanism for bridging the micro/macro divide, namely markets for buying stuff and elections for politicians. But most of the world doesn’t have those formal mechanisms, or indeed they have a fictive shadow of those things. For the most part we need to know enough about the actual social network to know who has the power and influence to bring about change.

Kelly claims that the world is a network much more than it’s a bunch of cases with attributes. For example, if you only understand how individuals behave, how do you tie things together?

History of social network analysis

Social network analysis basically comes from two places: graph theory, where Euler solved the Seven Bridges of Konigsberg problem, and sociometry, started by Jacob Moreno in the 1970’s, just as early computers got good at making large-scale computations on large data sets.

Social network analysis was germinated by Harrison White, emeritus at Columbia (emeritus), contemporaneously with Columbia sociologist Robert Merton. Their essential idea was that people’s actions have to be related to their attributes, but to really understand them you also need to look at the networks that enable them to do something.

Core entities for network models

Kelly gave us a bit of terminology from the world of social networks:

• actors (or nodes in graph theory speak): these can be people, or websites, or what have you
• relational ties (edges in graph theory speak): for example, an instance of liking someone or being friends
• dyads: pairs of actors
• triads: triplets of actors; there are for example, measures of triadic closure in networks
• subgroups: a subset of the whole set of actors, along with their relational ties
• group: the entirety of a “network”, easy in the case of Twitter but very hard in the case of e.g. “liberals”
• relation: for example, liking another person
• social network: all of the above

Types of Networks

There are different types of social networks.

For example, in one-node networks, the simplest case, you have a bunch of actors connected by ties. This is a construct you’d use to display a Facebook graph for example.

In two-node networks, also called bipartite graphs, the connections only exist between two formally separate classes of objects. So you might have people on the one hand and companies on the other, and you might connect a person to a company if she is on the board of that company. Or you could have people and the things they’re possibly interested in, and connect them if they really are.

Finally, there are ego networks, which is typically the part of the network surrounding a single person. So for example it could be just the subnetwork of my friends on Facebook, who may also know each other in certain cases. Kelly reports that people with higher socioeconomic status have more complicated ego networks. You can see someone’s level of social status by looking at their ego network.

What people do with these networks

The central question people ask when given a social network is, who’s important here?

This leads to various centrality measures. The key ones are:

1. degree – This counts how many people are connected to you.
2. closeness – If you are close to everyone, you have a high closeness score.
3. betweenness – People who connect people who are otherwise separate. If information goes through you, you have a high betweenness score.
4. eigenvector – A person who is popular with the popular kids has high eigenvector centrality. Google’s page rank is an example.

A caveat on the above centrality measures: the measurement people form an industry that try to sell themselves as the authority. But experience tells us that each has their weaknesses and strengths. The main thing is to know you’re looking at the right network.

For example, if you’re looking for a highly influential blogger in the muslim brotherhood, and you write down the top 100 bloggers in some large graph of bloggers, and start on the top of the list, and go down the list looking for a muslim brotherhood blogger, it won’t work: you’ll find someone who is both influential in the large network and who blogs for the muslim brotherhood, but they won’t be influential with the muslim brotherhood, but rather with transnational elites in the larger network. In other words, you have to keep in mind the local neighborhood of the graph.

Another problem with measures: experience dictates that, although something might work with blogs, when you work with Twitter you’ll need to get out new tools. Different data and different ways people game centrality measures make things totally different. For example, with Twitter, people create 5000 Twitter bots that all follow each other and some strategic other people to make them look influential by some measure (probably eigenvector centrality). But of course this isn’t accurate, it’s just someone gaming the measures.

Some network packages exist already and can compute the various centrality measures mentioned above:

• NodeXL, a plugin for Excel,
• NetworkX for python,
• igraph also for python,
• statnet for R, and
• Jure Leskovec at Stanford is creating new network package for C which should be awesome.

Thought experiment

You’re part of an elite, well-funded think tank in DC. You can hire people and you have $10million to spend. Your job is to empirically predict the future political evolution of Egypt. What kinds of political parties will there be? What is the country of Egypt gonna look like in 5, 10, or 20 years? You have access to exactly two of the following datasets for all Egyptians:

1. The Facebook network,
2. The Twitter network,
3. A complete record of who went to school with who,
4. The SMS/phone records,
5. The network data on members of all political organizations and private companies, and
6. Where everyone lives and who they talk to.

Note things change over time- people might migrate off of Facebook, or political discussions might need to go underground if blogging is too public. Facebook alone gives a lot of information but sometimes people will try to be stealth. Phone records might be better representation for that reason.

If you think the above is ambitious, recall Siemens from Germany sold Iran software to monitor their national mobile networks. In fact, Kelly says, governments are putting more energy into loading field with allies, and less with shutting down the field. Pakistan hires Americans to do their pro-Pakistan blogging and Russians help Syrians.

In order to answer this question, Kelly suggests we change the order of our thinking. A lot of the reasoning he heard from the class was based on the question, what can we learn from this or that data source? Instead, think about it the other way around: what would it mean to predict politics in a society? what kind of data do you need to know to do that? Figure out the questions first, and then look for the data to help me answer them.

Morningside Analytics

Kelly showed us a network  map of 14 of the world’s largest blogospheres. To understand the pictures, you imagine there’s a force, like a wind, which sends the nodes (blogs) out to the edge, but then there’s a counteracting force, namely the links between blogs, which attach them together.

Here’s an example of the arabic blogosphere:

The different colors represent countries and clusters of blogs. The size of each dot is centrality through degree, so the number of links to other blogs in the network. The physical structure of the blogosphere gives us insight.

If we analyze text using NLP, thinking of the blog posts as a pile of text or a river of text, then we see the micro or macro picture only – we lose the most important story. What’s missing there is social network analysis (SNA) which helps us map and analyze the patterns of interaction.

The 12 different international blogospheres, for example, look different. We infer that different societies have different interests which give rise to different patterns.

But why are they different? After all, they’re representations of some higher dimensional thing projected onto two dimensions. Couldn’t it be just that they’re drawn differently? Yes, but we do lots of text analysis that convinces us these pictures really are showing us something. We put an effort into interpreting the content qualitatively.

So for example, in the French blogosphere, we see a cluster that discusses gourmet cooking. In Germany we see various blobs discussing politics and lots of weird hobbies. In English we see two big blobs [mathbabe interjects: gay porn and straight porn?] They turn out to be conservative vs. liberal blogs.

In Russian, their blogging networks tend to force people to stay within the networks, which is why we see very well defined partitioned blobs.

The proximity clustering is done using the Fruchterman-Reingold algorithm, where being in the same neighborhood means your neighbors are connected to other neighbors, so really a collective phenomenon of influence.. Then we interpret the segments. Here’s an example of English language blogs:

Think about social media companies: they are each built around the fact that they either have the data or that they have a toolkit – a patented sentiment engine or something, a machine that goes ping.

But keep in mind that social media is heavily a product of organizations that pay to move the needle (i.e. game the machine that goes ping). To decipher that game you need to see how it works, you need to visualize.

So if you are wondering about elections, look at people’s blogs within “the moms” or “the sports fans”. This is more informative than looking at partisan blogs where you already know the answer.

Kelly walked us through an analysis, once he has binned the blogosphere into its segments, of various types of links to partisan videos like MLK’s “I have a dream” speech and a gotcha video from the Romney campaign. In the case of the MLK speech, you see that it gets posted in spurts around the election cycle events all over the blogosphere, but in the case of the Romney campaign video, you see a concerted effort by conservative bloggers to post the video in unison.

That is to say, if you were just looking at a histogram of links, a pure count, it might look as if it had gone viral, but if you look at it through the lens of the understood segmentation of the blogosphere, it’s clearly a planned operation to game the “virality” measures.

Kelly also works with the Berkman Center for Internet and Society at Harvard. He analyzed the Iranian blogosphere in 2008 and again in 2011 and he found much the same in terms of clustering – young anti-government democrats, poetry, conservative pro-regime clusters dominated in both years.

However, only 15% of the blogs are the same 2008 to 2011.

So, whereas people are often concerned about individuals (case-attribute model), the individual fish are less important than the schools of fish. By doing social network analysis, we are looking for the schools, because that way we learn about the salient interests of the society and how those interests are they stable over time.

The moral of this story is that we need to focus on meso-level patterns, not micro- or macro-level patterns.

John Bruner

Our second speaker of the night was John Bruner, an editor at O’Reilly who previously worked as the data editor at Forbes. He is broad in his skills: he does research and writing on anything that involved data. Among other things at Forbes, he worked on an internal database on millionaires on which he ran simple versions of social media dynamics.

Writing technical journalism

Bruner explained the term “data journalism” to the class. He started this by way of explaining his own data scientist profile.

First of all, it involved lots of data viz. A visualization is a fast way of describing the bottomline of a data set. And at a big place like the NYTimes, data viz is its own discipline and you’ll see people with expertise in parts of dataviz – one person will focus on graphics while someone else will be in charge of interactive dataviz.

CS skills are pretty important in data journalism too. There are tight deadlines, and the data journalist has to be good with their tools and with messy data (because even federal data is messy). One has to be able to handle arcane formats or whatever, and often this means parcing stuff in python or what have you. Bruner uses javascript and python and SQL and Mongo among other tools.

Bruno was a math major in college at University of Chicago, then he went into writing at Forbes, where he slowly merged back into quantitative stuff while there. He found himself using mathematics in his work in preparing good representations of the research he was uncovering about, for example, contributions of billionaires to politicians using circles and lines.

Statistics, Bruno says, informs the way you think about the world. It inspires you to write things: e.g., the “average” person is a woman with 250 followers but the median open twitter account has 0 followers. So the median and mean are impossibly different because the data is skewed. That’s an inspiration right there for a story.

Bruno admits to being a novice in machine learning.However, he claims domain expertise as quite important. With exception to people who can specialize in one subject, say at a governmental office or a huge daily, for smaller newspaper you need to be broad, and you need to acquire a baseline layer of expertise quickly.

Of course communications and presentations are absolutely huge for data journalists. Their fundamental skill is translation: taking complicated stories and deriving meaning that readers will understand. They also need to anticipate questions, turn them into quantitative experiments, and answer them persuasively.

A bit of history of data journalism

Data journalism has been around for a while, but until recently (computer-assisted reporting) was a domain of Excel power users. Still, if you know how to write an excel program, you’re an elite.

Things started to change recently: more data became available to us in the form of API’s, new tools and less expensive computing power, so we can analyze pretty large data sets on your laptop. Of course excellent viz tools make things more compelling, flash is used for interactive viz environments, and javascript is getting way better.

Programming skills are now widely enough held so that you can find people who are both good writers and good programmers. Many people are english majors and know enough about computers to make it work, for example, or CS majors who can write.

In big publications like the NYTimes, the practice of data journalism is divided into fields: graphics vs. interactives, research, database engineers, crawlers, software developers, domain expert writers. Some people are in charge of raising the right questions but hand off to others to do the analysis. Charles Duhigg at the NYTimes, for example, studied water quality in new york, and got a FOIA request to the State of New York, and knew enough to know what would be in that FOIA request and what questions to ask but someone else did the actual analysis.

At a smaller place, things are totally different. Whereas the NYTimes has 1000 people on its newsroom floor, the Economist has maybe 130, and Forbes has 70 or 80 people in their newsrooms. If you work for anything beside a national daily, you end up doing everything by yourself: you come up with question, you go get the data, you do the analysis, then you write it up.

Of course you also help and collaborate with your colleagues when you can.

Advice Bruno has for the students in initiating a data journalism project: don’t have a strong thesis before you’ve interviewed the experts. Go in with a loose idea of what you’re searching for and be willing to change your mind and pivot if the experts lead you in a new and interesting direction.