31 Oct 2014

R: Converting a named vector to a data frame

I’ve been playing around with igraph’s page rank function to see who the most central nodes in the London NoSQL scene are and I wanted to put the result in a data frame to make the data easier to work with.

I started off with a data frame containing pairs of people and the number of events that they’d both RSVP’d 'yes' to:

> library(dplyr)
> data %>% arrange(desc(times)) %>% head(10)
       p.name     other.name times
1  Amit Nandi Anish Mohammed    51
2  Amit Nandi Enzo Martoglio    49
3       louis          zheng    46
4       louis     Raja Kolli    45
5  Raja Kolli Enzo Martoglio    43
6  Amit Nandi     Raja Kolli    42
7       zheng Anish Mohammed    42
8  Raja Kolli          Rohit    41
9  Amit Nandi          zheng    40
10      louis          Rohit    40

I actually had ~ 900,000 such rows in the data frame:

> length(data[,1])
[1] 985664

I ran page rank over the data set like so:

g = graph.data.frame(data, directed = F)
pr = page.rank(g)$vector

If we evaluate pr we can see the person’s name and their page rank:

> head(pr)
Ioanna Eirini          Mjay       Baktash      madhuban    Karl Prior   Keith Bolam
    0.0002190     0.0001206     0.0001524     0.0008819     0.0001240     0.0005702

I initially tried to convert this to a data frame with the following code...

> head(data.frame(pr))
                     pr
Ioanna Eirini 0.0002190
Mjay          0.0001206
Baktash       0.0001524
madhuban      0.0008819
Karl Prior    0.0001240
Keith Bolam   0.0005702

...which unfortunately didn’t create a column for the person’s name.

> colnames(data.frame(pr))
[1] "pr"

Nicole pointed out that I actually had a named vector and would need to explicitly extract the names from that vector into the data frame. I ended up with this:

> prDf = data.frame(name = names(pr), rank = pr)
> head(prDf)
                       name      rank
Ioanna Eirini Ioanna Eirini 0.0002190
Mjay                   Mjay 0.0001206
Baktash             Baktash 0.0001524
madhuban           madhuban 0.0008819
Karl Prior       Karl Prior 0.0001240
Keith Bolam     Keith Bolam 0.0005702

We can now sort the data frame to find the most central people on the NoSQL London scene based on meetup attendance:

> data.frame(prDf) %>%
+   arrange(desc(pr)) %>%
+   head(10)
             name     rank
1           louis 0.001708
2       Kannappan 0.001657
3           zheng 0.001514
4    Peter Morgan 0.001492
5      Ricki Long 0.001437
6      Raja Kolli 0.001416
7      Amit Nandi 0.001411
8  Enzo Martoglio 0.001396
9           Chris 0.001327
10          Rohit 0.001305

About the author

I'm currently working on short form content at ClickHouse. I publish short 5 minute videos showing how to solve data problems on YouTube @LearnDataWithMark. I previously worked on graph analytics at Neo4j, where I also co-authored the O'Reilly Graph Algorithms Book with Amy Hodler.