Algorithms For Dummies

3

Exploring the 

World of Graphs

---

IN THIS PART . . .

Discover graph essentials that help you draw, measure, 

and analyze graphs.

Interact with graphs to locate nodes, sort graph 

elements, and find the shortest path.

Work with social media in graph form.

Explore graphs to find patterns and make decisions 

based on those patterns.

Use the PageRank algorithm to rate web pages.

---

CHAPTER 8

  Understanding Graph Basics 

     155

IN THIS CHAPTER

 

» Defining why networks are important

 

» Demonstrating graph drawing 

techniques

 

» Considering graph functionality

 

» Using numeric formats to represent 

graphs

Understanding 

Graph Basics

G

raphs are structures that present a number of nodes (or vertexes) con-

nected by a number of edges or arcs (depending on the representation). 

When you think about a graph, think about a structure like a map, where 

each location on the map is a node and the streets are the edges. This presentation 

differs  from  a  tree  where  each  path  ends  up  in  a  leaf  node.  Remember  from 

Chapter 7 that a tree could look like an organizational chart or a family hierarchy. 

Most important, tree structures actually do look like trees and have a definite start 

and a definite end. This chapter begins by helping you understand the importance 

of networks, which are a kind of graph commonly used for all sorts of purposes.

You can represent graphs in all sorts of ways, most of them abstract. Unless you’re 

really good at visualizing things in your mind (most people aren’t), you need to 

know how to draw a graph so you can actually see it. People rely on their vision to 

understand how things work. The act of turning the numbers that represent a 

graph into a graphic visualization is plotting. Languages like Python excel at plot-

ting because it’s such an incredibly important feature. In fact, it’s one of the rea-

sons that this book uses Python rather than another language, such as C (which is 

good at performing a completely different set of tasks).

After you can visualize a graph, it’s important to know what to do with the graphic 

representation.  This  chapter  starts  you  off  by  measuring  graph  functionality. 

Chapter 

8

---

156

 

   

  PART 3