Matt Dray (@mattdray)
Relay FM is a network that focuses largely on tech content1. It was started by Myke Hurley and Stephen Hackett in 2014 and you can find a list of shows and personnel on their site. Many of Relay FM’s hosts have hosted more than one podcast within the network. What do the relationships between them look like?
This post is about preparing and visualising this ‘Relayverse’ using the R packages
tidygraph for network data handling and
ggraph for network visualisation (both by Thomas Lin Pedersen), along with the
visNetwork package (from Benoit Thieurmel and Titouan Robert of Datastorm, wrapping Almende BV’s
vis.js library) for interactive visualisation.
Scroll to the bottom to find the interactive tool if you aren’t interested in the code.
I’m using two suites of ‘tidy’ packages in this post: one set for data collection and manipulation, and one set for graph network building, analysis and visualisation.
read_html() gets the HTML for the selected page;
html_node() identifies which element needs to be scraped2; and
html_table() interprets the HTML information as a dataframe. I’ve removed the show ‘B-Sides’ because it’s clips from other shows.
# Get the HTML for the selected page relay_wiki <- read_html("https://en.wikipedia.org/wiki/Relay_FM") # Get the table with current shows current <- relay_wiki %>% html_node(xpath = '//*[@id="mw-content-text"]/div/table') %>% html_table() %>% filter( !Podcast %in% c("Members Only", 'Paid "Members Only" Shows', "B-Sides") ) %>% mutate(Status = "Current") # label rows as current shows # Get the table with retired shows retired <- relay_wiki %>% html_node(xpath = '//*[@id="mw-content-text"]/div/table') %>% html_table() %>% select(-`Number of episodes`) %>% mutate(Status = "Retired") # label rows as retired shows # Combine the tables into one dataframe shows <- bind_rows(current, retired) # Look at a few random hosts/podcasts from the table select(shows, Podcast, Hosts) %>% sample_n(5) %>% knitr::kable()
|12||Liftoff||Jason SnellStephen M. Hackett|
|5||Upgrade||Myke HurleyJason Snell|
|30||Fusion||Stephen M. Hackett|
|3||The Pen Addict||Myke HurleyBrad Dowdy|
Unfortunately the host names are in the form ‘First LastFirst Last’ so we need a regular expression to split the string where a lowercase letter meets an uppercase letter3. This leaves us with a list column that we can
unnest() to get one row per podcast-host combination.
# Clean the host names shows_clean <- shows %>% mutate( Hosts = str_remove_all(Hosts, " \\(originally\\)"), Hosts = str_split(Hosts, "(?<=[a-z])(?=[A-Z])") ) %>% unnest() %>% select(Podcast, Hosts, Status) # Print a random sample of 10 sample_n(shows_clean, 10) %>% knitr::kable()
|64||CMD Space||Myke Hurley||Retired|
|6||The Pen Addict||Myke Hurley||Current|
Our dataframe is now tidy and ready for Tidygraph, but before moving on, we can do things like look at the host with the most active shows.
shows_clean %>% filter(Status == "Current") %>% count(Hosts) %>% filter(n > 2) %>% arrange(desc(n)) %>% knitr::kable()
|Stephen M. Hackett||5|
Or out of interest, the shows that have had the most hosts.
shows_clean %>% count(Podcast) %>% arrange(desc(n)) %>% slice(1:6) %>% knitr::kable()
an entry into the tidyverse that provides a tidy framework for all things relational (networks/graphs, trees, etc)
To use the package, we need every host combination4 for each podcast, which can be achieved with the
combn() function. This gives us a pair of points (‘nodes’ in graph-speak) that can be connected by a line (an ‘edge’) to indicate their relationship.
But a show with one host doesn’t have a pair of points, so I’m going to duplicate these rows first. If we don’t do this, we can’t plot these shows because they won’t have a connection between two nodes.
# Isolate the shows with one host solo_vec <- shows_clean %>% count(Podcast) %>% filter(n == 1) %>% pull(Podcast) # Filter the show-host dataframe by solo-hosted podcasts solo_df <- filter(shows_clean, Podcast %in% solo_vec)
Now we can bind these rows to the data and then get our host combinations. Big shout out to William Chase for a solution to getting all combinations of elements within some parent element (e.g. hosts within podcasts).
# Prepare host combinations per show relay_combos <- shows_clean %>% bind_rows(solo_df) %>% # to duplicate the shows with solo hosts group_by(Podcast) %>% # operate within each podcast split(.$Podcast) %>% # split on podcast map(., 2) %>% # gets vector of hosts per podcast list element map(~combn(.x, m = 2)) %>% # all pair combiantions map(~t(.x)) %>% # transpose the matrix map(as_tibble) %>% # convert to a tibble dataframe bind_rows(.id = "Podcast") %>% # list-element name to column select(V1, V2, Podcast) sample_n(relay_combos, 10) %>% knitr::kable() # random sample of 10
|Federico Viticci||Stephen M. Hackett||The Prompt|
|Brianna Wu||Mikah Sargent||Isometric|
|Myke Hurley||Tiffany Arment||Playing for Fun|
|Federico Viticci||Stephen M. Hackett||Connected|
|Brianna Wu||Georgia Dow||Isometric|
|Federico Viticci||Myke Hurley||Remaster|
|Brianna Wu||Mikah Sargent||Disruption|
|Myke Hurley||Myke Hurley||Inquisitive|
|Federico Viticci||Fraser Spiers||Canvas|
|Jason Snell||Jason Snell||Download|
We can turn this dataframe of host-pair combinations into a tidygraph object with the
as_tbl_graph() function. This class of object contains two dataframes (the nodes and the edges) and some metadata.
We can also use functions from the
tidygraph package to help calculate various network statistics. For example, the
centrality_degree() function tells us the nodes with the most connections. We can add this as a column in our node data and use this later to do things like resize nodes depending on their centrality.
You can manipulate the nodes and edges dataframes in this tidygraph object by using the
activate() function to switch between them. Currently the node data are active (it says ‘active’ above the nodes dataframe), so our application of
centrality_degree() to the network object will affect the node data specifically.
relay_graph <- as_tbl_graph(relay_combos, directed = FALSE)%>% mutate(connections = centrality_degree()) %>% # number of connections arrange(desc(connections)) # order by number of shows print(relay_graph)
## # A tbl_graph: 40 nodes and 66 edges ## # ## # An undirected multigraph with 8 components ## # ## # Node Data: 40 x 2 (active) ## name connections ## <chr> <dbl> ## 1 Myke Hurley 21 ## 2 Stephen M. Hackett 10 ## 3 Brianna Wu 9 ## 4 Mikah Sargent 9 ## 5 Federico Viticci 8 ## 6 Georgia Dow 7 ## # … with 34 more rows ## # ## # Edge Data: 66 x 3 ## from to Podcast ## <int> <int> <chr> ## 1 9 9 Almanac ## 2 1 32 Analog(ue) ## 3 11 33 Automators ## # … with 63 more rows
The edges and nodes are now in the same object. You can see we have a 40 nodes and 66 edges and that the netowrk is undirected (nodes don’t ‘point’ to each other). We also have eight ‘components’, which are the isolated groups of nodes that connect to each other, but not to other groups.
ggraph package was designed to work seamlessly with
tidygraph objects and the
ggplot2 plotting package. You simply pass your
tidygraph object to
ggraph‘s ’graph’ argument. Below are a couple of examples for demonstration purposes that show you just a handful of options. You can learn more about
ggraph’s layouts, nodes and edges in a series of blog posts from Thomas Lin Pedersen.
This example arranges the nodes (hosts) circularly (plot A) and a straight line (B) and sizes them by the number of connections to other hosts. Each line (edge) represents a co-hosting relationship.
g1 <- ggraph( graph = relay_graph, layout = "linear", circular = TRUE ) + geom_node_point(aes(size = connections)) + geom_edge_arc() + theme_void() + theme(legend.position = "none") g2 <- ggraph( graph = relay_graph, layout = "linear" ) + geom_node_point(aes(size = connections)) + geom_edge_arc() + theme_void() + theme(legend.position = "none") plot_grid(g1, g2, labels = c("A", "B"))
This example arranges the nodes (hosts) according to an algorithm specified by the
layout argument to
ggraph() and sizes them by the number of connections to other hosts. Each line (edge) represents a co-hosting relationship and multiple connections are shown separately by ‘fanning’ them out (hence the
ggraph(graph = relay_graph, layout = "nicely") + geom_node_point(aes(size = connections)) + geom_edge_fan() + theme_void() + theme(legend.position = "none")
I haven’t added labels on the nodes nor the points because of the visual clutter it creates for this particular example. You could use
geom_node_text() to add node labels and something like
aes(label = <column_name>) in your edge geom to label the connections.
This is where interactive network graphs come in handy, as you can zoom, pan and hover to get more info.
visNetwork package wraps the
vis.js library to make interactive network graphs. Its
visNetwork() function takes separate dataframes of edges and nodes that are in a pre-specified format, so we won’t be able to use our tidygraph object for this.
# Dataframe of unique nodes with an ID value nodes <- shows_clean %>% # take our podcast-host dataset distinct(Hosts) %>% # get column of unique hosts arrange(Hosts) %>% # alphabetical order mutate(id = as.character(row_number()), label = Hosts) %>% select(-Hosts) #%>% # provides pop up value on viz # Dataframe of 'origin' and 'destination' nodes for edge drawing edges <- relay_combos %>% left_join(nodes, by = c("V1" = "label")) %>% left_join(nodes, by = c("V2" = "label")) %>% rename(from = id.x, to = id.y, title = Podcast)
Now we can just plug the data into the
visNetwork() function and pipe this into some other other functions to set some options.
visNetwork(nodes, edges, main = "The Relayverse", submain = "Nodes are hosts, edges are shows" ) %>% visOptions( highlightNearest = TRUE, # on-hover highlight nearest nodes nodesIdSelection = TRUE # select node from dropdown ) %>% visInteraction(navigationButtons = TRUE) %>% # easy-navigation buttons visPhysics( # set physics 'engine' and options solver = "forceAtlas2Based", forceAtlas2Based = list(gravitationalConstant = -50) ) %>% visLayout(randomSeed = 1337) # reproduce the same network each time
- use the navigation buttons or your trackpad/mouse to navigate the network
- click a node to highlight a host and their co-hosts
- hover over an edge to show a label with the show name
- select a host from the dropdown menu to highlight them and their co-hosts
- click and drag a node to move it
This is a very simple example, but lots of other
visNetwork options are available.
This was really just an introduction to
visNetwork. These packages make network analysis a little more consistent and can provide some interesting stats and visuals very quickly. A next step might be to produce a ‘network of podcast networks’, since Relay FM hosts appear in shows on other networks as well.
(?<=[a-z])(?=[A-Z])can be interpreted as ‘split after but not including (
?<=) a lowercase letter (
[a-z]), and before but not including (
?=) a capital letter (
We want combinations, not permutations. ‘Federico Viticci to Stephen M. Hackett’ is the same as ‘Stephen M. Hackett to Federico Viticci’, for example.↩