In general, pie charts should be used only when the number of categories is small and the relative sizes of the different slices can be easily determined.
If you have several categories, use a column or bar chart.
Line charts are best for categories that follow a sequential order.
Be aware, however, that the time intervals must be a constant length if used in a line chart.
Line charts will distort data that occurs in irregular time intervals, making it appear that the data values occurred at regular intervals when they did not. Pie, column, bar, and line charts assume that numbers are plotted against categories. In science and engineering applications, you will often want to plot two numeric values against one another. For that data, use XY scatter charts, which show the patterns or relationship between two or more sets of values. XY scatter charts are also good for data recorded at irregular time intervals. If you still can't find the right chart to meet your needs, you can create a custom chart based on the built- in chart types. Third-party vendors also sell software to allow Excel to create charts not built into the software.