2.2 Bar Charts
This lesson is all about Bar charts. Bar charts, also called column graphs, can be used to measure quantities over time and examine trends, like a line chart can, but they often deal with discreet quantities of things at a particular time, or in a particular group. They are useful when comparing the same data between similar entities, for example the number of tornadoes in each US state over a period of time.
Bar charts can display both positive and negative values, and can also be used to chart progress. The bars can be either horizontal or vertical, and usually with horizontal bars, the value and category axes are flipped from their orientation on a line chart.
So let’s make some Bar charts the right way!
- Always, always have a zero baseline: There are no exceptions to this rule. You can sometimes get away with starting somewhere else in a line chart, but when you truncate the bars in a bar graph, you mis-represent the data.
- Double-check your data: If you see something that doesn’t look quite right, go back to the source. This is true for all types of charts, of course. The graphic is only as good as the data on which it is built.
- Don’t use a double bar graph that go in different directions: In the west, anyway, numbers to the left of zero are negative.
- Always sort the data in a horizontal bar graph in numerical order: An exception is when you have a list that is typically displayed alphabetically.
- Stay away from neon colors
- Don’t alternate lights and darks: It gives people a headache. Put the shades in order from light to dark.
- Don’t use 3D: It has no meaning and it distorts the data.
- Stay away from decorations or textures: You may be tempted to turn your bars into flowers or pencils or barrels of oil, and it’s true that yours truly created a tutorial on how to do just this sort of thing. But I am telling you now it’s all just decoration, not information. So don’t do it!