Building Bar Graphs
Bar graphs can be used to show how something changes over time or to compare different times. Bar graphs are good for plotting data that spans many years (or days, weeks . . .), has really big changes from year to year (or day to day . . .), or they can be used for comparing different items in a related category (for example: comparing something between different states). The following pages describe the different parts of a bar graph.
The title offers a short explanation of what is in your graph. This helps the reader identify what they are about to look at. It can be creative or simple as long as it tells what is in the graph. The title of this graph tells the reader that the graph contains information about the states with the most elementary and secondary schools, and how many schools each of those states has.
The legend tells us what each bar represents. Just like on a map, the legend helps the reader understand what they are looking at. This legend tells us that the blue bars represent elementary and secondary schools. If a graph has more than one color bar, the legend will have more than one entry.
The source explains where you found the information that is in your graph. It is important to give credit to those who collected your data! In this graph, the source tells us that we found our information from the NCES Common Core of Data.
Bar graphs have an x-axis and a y-axis. In most bar graphs, like the one above, the x-axis runs horizontally (flat). Sometimes bar graphs are made so that the bars are sidewise like in the graph below. Then the x-axis has numbers representing different time periods or names of things being compared. In these graphs, the x-axis has names of states.
In most bar graphs, like the one above, the y-axis runs vertically (us and down). Sometimes bar graphs are made so that the bars are sideways like in the graph to the left. Then the y-axis is horizontal (flat). Typically, the y-axis has numbers for the amount of stuff being measured. The y-axis usually starts counting at 0 and can be divided into as many equal parts as you want to. In these bar graphs, the y-axis is measuring the number of schools.
The most important part of your graph is the information, or data, it contains. Bar graphs can present data in many ways and can present more than one group of data at a time. The graph on the left is a regular bar graph with one group of data. The center graph has two groups of data that are stacked. The graph on the right is another graph with two groups of data, but they are presented side by side instead of stacked.