Don’t read this if you haven’t read Harry Potter yet! But in that case: shame on you!
My dearest Kartoffelköpfchens,
These last months, this jetsetter has been travelling the world, spreading the word of our spaghettilicous Overlord, from Paris to Padua to Florence (Ok, I admit, that’s not really impressive on a global scale… But you can’t blame me for all those trips to Italy: it’s pasta heaven over here!).
But with summer almost over, I think it’s time to remind you beach bums and party addicts that there’s more to life than tans, summer flings and alcohol. Networks in particular, of course, cuz that’s what we’re here for. A while back, a waaaay big whale of a while back (I saw a whale once. On a boat trip off the coast of Boston. Was sick to the bones. Two weeks ago I saw a dolphin. On a boat trip off the coast of Ireland. Was sick to the bones. Coincidence? Yeah, why not), I told you I was playing around with Gephi’s timeline feature. We’ll, today I’m gonna show you how that works, because it’s an indispensible feature for any historian who’s into serious network analysis.
Gephi Timeline Basics
To activate Gephi’s timeline, you need a nodelist and an edgelist, just like for a static network (if you’re not sure how that works anymore, check out this post on the basics of Gephi). All you need to do actually, is add a time interval to both. The nodelist time interval tells Gephi when specific nodes appear and disappear in the network (e.g. the birth and death of a person); the edgelist time interval tells Gephi at what point in time a relation between two specific nodes was present.
There are two ways to set up these time intervals: either you format the time interval column yourself in your database, so they’re up and ready in your .csv file, or you let Gephi create the time interval.
Now, don’t panic. I’ll take you through it.
Gephi Timeline Basics: setting up the time interval in Gephi
This is the info a basic nodelist needs to create a time interval: your node IDs, your nodes, a start date, and an end date. I used years but you can also enter dates in the dd-mm-yyyy format if your data is more precise.
After importing the nodelist into the Data Laboratory, you can create a time interval by merging your start and end date columns.
A pop-up appears where you can select the relevant columns, and in the drop-down menu you select the option ‘Create time interval’.
Click ‘Ok’. (I should have called this post ‘Time intervals for Dummies’…)
A new pop-up appears where you can set certain parameters. Since I often work with BC dates, I generally choose the option ‘Parse numbers’ (BC dates are indicated with a minus sign in our database, so -230 = 230 BC). If you use a standard date format, however, you can opt for ‘Parse dates’. Make sure to select the correct start and end date columns at the top as well!
Tada! The time interval is now added to your nodelist.
This is the info a basic edgelist needs to create a time interval: your node IDs, the edge weight, the edge type, a start date, and an end date.
To create the time interval for your edgelist, follow the same steps as for the nodelist.
c) Adjusting the timeline settings
Now, when you go to the overview pane, at the bottom in the middle of the screen, you’ll see a button that says ‘Enable Timeline’. Do I really have to say it? Click on it! A timeline should now appear.
To adjust the settings, click on the wheel in the bottom left corner of the timeline.
There are two important things you can customize: the bounds of your timeline, and the animation settings.
When setting the bounds, you can select the start and end date you want for your timeline, and at the same time you can adjust the length of your time interval. The standard settings select the entire time frame, so to see the network evolve you need to set a more limited time interval. You can do so in the ‘custom time bounds’ pop up, but also by dragging the selection in the timeline itself.
You can also change the speed of the timeline animation. It’s generally set to 100ms, but then things tend to go really fast if you’re working with years, like I do, so I increase this to 300 or so to slow it down a bit.
And that’s all there is to it. All you have to do now is click on the play button. If you want to check out the result, watch the movie.
Yes! Another Harry Potter network! (Sorry for the terrible quality… I’ll try to stream it from a different server as soon as possible)
It starts in year 1979 of the Muggle era. Only those wizards that were already born at the time are visible at the start in this network. Links are scarce: Fred & George, since they’re brothers, and Dumbledore & Hagrid, since they work together at Hogwarts. Then Cho is born, and a year later Harry, Hermione and Ron, who is linked to his two brothers. In 1981 Ginny’s born, which creates new links in the Weasley family cluster. From 1991 onwards, things speed up: as Harry, Ron and Hermione start to attend Hogwarts, more links appear, both among the students as well as between them and the teachers. In their third year, Lupin shortly becomes connected, since he teaches Defense against the Dark Arts, and Harry finally meets his godfather Sirius. Unfortunately, Bellatrix killed him in the Battle of the Department of Mysteries in 1996, so he disappears from the network then. Same goes for Dumbledore when he’s killed by Draco in 1997…
*choking back tears*
*whispers* I think that’s enough for today…
*nostalgically starts looking up Dumbledore gifs*