About chart typesYou can use charts to compare data graphically. For example, bar charts give a good overall picture of your data set, but they are difficult to read when there are numerous bars. Bar charts also imply that data values are frozen. If your data continuously changes over time, a line chart might be a better choice. If you want to compare the percentage of one data series (a single bar) to the sum of all data series (all the bars), a pie chart works well.