Hello Steemians,
this is a visualization guide from your best data visualization friend datatreemap :-)
It is a guide on how to visualize a graph in R by using the igraph package. A graph can be visualized starting from its adjacency matrix data which shows what are the nodes of the graph and how are they connected. Here you can read more about it Adjacency Matrix
In my case, my adjacency matrix contains the following data:
"Milan","London","Berlin","Rome","Copenhagen","Paris","Moskow","Istambul"
"Milan",0,0,0,0,0,0,0,0
"London",0,0,0,0,0,1,1,0
"Berlin",0,0,0,0,1,0,0,0
"Rome",0,0,0,0,0,0,1,0
"Copenhagen",0,0,1,0,0,0,0,0
"Paris",0,1,0,0,0,0,0,0,
"Moskow",0,1,0,1,0,0,0,1
"Istambul",1,1,1,0,0,0,0,0
These are the data that show if a city is connected with another city through a flight. So the data says that there is a flight from Berlin to Copenhagen but there is no flight from Copenhagen to Moscow.
For visualizing this information as a graph we need an R package called igraph. So let's install it and load the dataset in a matrix we call traffic.txt:
install.packages("igraph") ## install igraph
library(igraph) ## load the package
flightmatrix <- as.matrix(read.csv("C:\Users\Alket\Documents\traffic.txt"))
So what the above code does is installing the igraph package and using it or the current R session. Then with the third line the code loads the data in the "flightmatrix" object.
Now, let's model the flights as connections between cities. We will use the igraph package for this modeling and in particular the adjacency() function as in the following lines. More on this we will use an undirected graph as you can see from the mode = "undirected"
flight <- graph.adjacency(flightmatrix,mode="undirected", diag=FALSE)
set.seed(1)
And then plot the results of the flight modeling by giving to the nodes a red color and labels a black one.
plot(flight,layout=layout.fruchterman.reingold,
vertex.label=V(flight)$name,vertex.color="red",vertex.label.color="black",vertex.frame.color=0,vertex.label.cex=1.5)
And here is the result below. As you can see it is fairly easy to visualize a graph with R and the igraph package.
If you liked this guide datatreemap will soon come up with more so stay tuned.