Gephi focus on data import. Clément Levallois Gephi Support Team and Assist.

Transcription

1 Gephi focus on data import Clément Levallois Gephi Support Team and Assist. V 1.2 Sept

2 Bio notes Education in economics, management, history of science (Ph.D.) Turned to digital methods for research. data visualization, network analysis, natural language processing, web applications and more. Member of the Gephi Community Support team Gephi certified trainer Contact, feedback welcome: on or 2

3 1. Network already formed 3

4 Network already formed? Import is direct 4

5 Network data in Excel format - Via the data laboratory - Needs at least a list of edges - If you don t have a list of nodes, they will be created automatically fro the nodes mentioned in the edges list - just tick the option for nodes creation when prompted in the edge import wizzard! 5

6 Frequent mistakes when importing data in the data lab: - Take extra caution with the headers (first line) of your files! At least: - For edges: Source,Target - For nodes: Id,Label - Take extra caution with the format of fields! - Check that your numeric attributes (as opposed to textual) are not imported as «String» (which means text), but as numbers indeed (Float, Double or Integer) - If you import a list of nodes and edges - Import the list of nodes first! - If you import a list of edges only - Check that the option for the creation of missing nodes is selected 6

7 2. Data not in network format yet 7

8 The general idea 8

9 The steps YOU START WITH List / table of observations 1. Extract connected entities (a network!) 2. Format this network in a conventional standard Not many solutions! Many solutions 3. Display the network with a software package / in the browser Many solutions 9

10 Gaze: similarity computer Network connecting universities, with weak or strong ties depending on the similarity in terms of journals where these univ. publish Gaze can be downloaded from Available soon as a Gephi plugin (easier to use, works on Macs ) Contact me at [email protected] if you need it now. 10

11 Creating a network from cooccurrences data in Excel / CSV A plugin to install directly from Gephi (Tools -> Plugins) Network made of authors and literary agents Network of article co-authors See next slides for further instructions on how to use this plugin Network formed by co-authors and the journals where they publish 11

12 1. Install the Plugin 1. Tools -> Plugin 2. Select Convert Excel and csv files in the tab Available plugins, then install it and restart Gephi 12

13 2. Select Import Spigot, then Data importer and follow the wizzard 13

14 Example of a dataset This Excel file can be converted into a network where: - Followers are connected to followers - Followers are connected to persons being followed - Time periods are taken into account. Note on proper formats for the Date column: - Can be an interval of dates, with the start date and end date separated by a comma (like above) - Can be an interval of years, also separated by a comma (2012,2014) - Can be a simple date ( ) or simple year (1979) 14

15 Create a dynamic network via the data laboratory Need two attributes for the nodes: An attribute containing the apparition date for the nodes Another one for the disappearance date for the nodes Use the fusion function to create a time interval from these 2 attributes (see next slide) Same principle to create dynamic edges. This approach has severe limits: only the topology of the network is dynamic, not the attributes (which stay fixed). And the dynamic topology is very limited a node can just appear and disappearm that s all. This is a case where a programmatic approach would bring much more flexibility. 15

16 The function Merge columns 2. Select the 2 columns which contain the dates of beginning and end (date or simple number, works as well) 3. Select Create time interval 1. Click on this button 16

17 Last step: create time interval It is possible to leave the end date empty. If your temporal data are in the format of a date, be cautious to register the correct format, failing to do so will crash the creation and probably need you to restart Gephi to reinitialize. That s all! You can then switch to the Overview, activate the timeline and animate the network 17

18 Next step: Gephi advanced functions 18