Visualizing data can have a tremendous impact compared to just printing raw numerical data. Adding a chart to a report makes it possible for readers to quickly grasp the important relationships between data. Many times reports are used with proposals to sell a reader on an idea or plan. Adding a colorful chart can sell your idea more effectively than a dry report filled with endless numbers. This chapter shows you what types of charts are available as well as how to modify their appearance so that they can make your report more appealing and quickly get your message across.
Choosing the Proper Chart
Charts are used to make it easy to compare sets of data. The visual aspect of a chart lets the reader immediately recognize things such as the differences in quantity, percentage of the whole or numerical trending. Depending upon the information you are trying to convey, certain chart styles are more effective at presenting this information than others. Table 10-1 lists different chart styles and what they are effective at presenting. This table gets you started in the right direction for choosing the proper chart.
Table 10-1. Effectiveness of different chart styles.
| Chart Style | Effective at … |
|---|---|
| Bar Chart | Comparing the differences between items and events. |
| Comparing items and events against the same scale without relation to time. | |
| Showing relationships between sets of data using grouping. | |
| Note: The X-axis is generally non-numeric. When it is numeric, the interval isn’t relevant. | |
| Line Chart/Area Chart | |
| Comparing continuous data over a period of time against a common scale. | |
| Tracking movement over time. | |
| Examining trends between two or more sets of data. | |
| Note: The X-axis represents a unit of time. | |
| X-Y Scatter Chart | Charting a large quantity of values without relation to time. |
| Finding groups of data where there is a large percentage of similar data points. | |
| Bubble Chart | Similar to the X-Y chart, but with a third data point. The third data point determines the bubble’s diameter. It is proportional to the value of this data point. |
| Pie/Doughnut Chart | Visualizing the percent of the whole. |
| Examining relationships as part-to-whole. | |
| Note: There is only a single axis being represented. Thus, only one value is being charted. | |
| Radar Chart | Comparing data sets in a star pattern. The importance/relationship of each data set is determined by having the target value start at either the center of the axis or the outside. |
| Stock Chart | Analyzing stock values. Shows the trading range for the day as well as first trade and last trade amounts. |
| 3D Surface Chart | Showing trends with relationship to time. |
| Note: It uses a three dimensional surface to make it easy to analyze a large quantity of data. |
To use Table 10-1, think about why you are using a chart to present your data, ask yourself, “What is the message I am trying to convey to the reader?” Scan the list of reasons of why one chart is more effective than the other charts. Once you see a description that best matches your purpose, select that type of chart.
For example, assume that you have a report that prints the annual sales for each division in a corporation. The message you are conveying is which division had the largest sales volume as well as which division had the lowest sales. Three charts that are good at comparing different data sets are the bar chart, the line chart and the X-Y chart. The bar chart immediately looks good because it is effective at comparing differences between items. The line chart also compares data, but it does so over a period of time. This doesn’t apply here because the data is within the same time period (i.e. the same year). So the line chart is not a good choice. The X-Y chart compares data, but it is done with respect to two data points. In other words, both the X and Y axis must represent numerical data. The sales report is charted with the sales volume and the division name. Since the division name isn’t numerical data, it can’t be used with the X-Y chart. The best choice for the division annual sales report is the bar chart.
Let’s build on this example by saying that you are given a new requirement where the report has to be modified so that it is now a drill-down report. It currently shows the annual sales per division and it needs to be modified so that you can drill-down on a division and see its monthly sales. This helps the reader determine if the division had a particular month that was exceptionally better than the other months or if the division was consistently improving. The purpose of this chart is very similar to the first chart. You want to tell the reader how the total sales compare to each other. But this example has a slight variation: you are now charting for a single division and the individual months are being compared to each other. You are working with data that changes over a period of time and looking for the trend. The only reason we didn’t use a line chart in the first example was because the data didn’t relate to time. This example does relate to time and it is also looking at the sales trend. So the line chart is an excellent choice for presenting the monthly sales figures.
