What Are Charts, and When Is It Appropriate to Use Pie, Column, Bar, and Line Charts?
Pie Charts or Circle Graphs
- Pie charts consist of subgroups that combine to form a whole unit. For example, to display the eye colors represented in a group of people, you would place everyone in a corresponding color group, with each group receiving a wedge of the pie sized according to the percentage of the total they represent. For instance, if blue-eyed people constitute 25 percent of the whole group, the blue-eyed group would have a wedge of the circle that was one-fourth the total area of the circle.
Bar Graphs or Column Graphs
- Bar graphs, which are also called column graphs, display observations made over time. They are best used to chart the change in one variable over time. For example, you would use a bar graph to chart the monthly rainfall in a set area during the course of a year. The height of the bars would correspond to the rainfall, and each month would have a bar that displays its rainfall total.
- Line charts show trends or relational correlations. For example, if a teacher wants to demonstrate that students' GPAs increase based on the number of hours they dedicate to studying, the teacher would number study hours on one side of the graph and GPA intervals on the other side of the graph, chart the students' figures, and then connect all the points with a line.
Ways to Make Graphs
- You can create charts by hand or electronically. Though these charts are simple enough to sketch to scale by hand, many word processing or other computer-based programs can create charts based on data you enter into the program. Though many math instructors require students to draw graphs by hand when learning about graph making, it is appropriate to use electronically generated graphs for other projects, when quoting mathematical figures unrelated to chart making.