When you create a graph, you are essentially creating a way of visualizing two or more characteristics of your data. For example, your graph may to attempt to visualize the date and numeric value of a data item. Or perhaps it depicts the quantities of certain data items as they relate to a category that the data item falls into (such as Expenditures or Revenues).
Scales and grids help pinpoint and classify these characteristics of your data. Scales, which are located along the sides and bottom of a graph, use a combination of tick marks and labels to indicate either the category, time period, or numeric value of each data item in the graph. The grid, meanwhile, consists of a number of evenly spaced vertical or horizontal lines in the background of the graph. These lines are extensions of the tick marks and scale labels, and can be used like a ruler to judge the value of data items in the graph.
Together, these features make it possible to visually determine the meaning of a data item. For example, by using the bottom scale in the graph below, you can easily determine that the first three bars are in the Group 1 category. Meanwhile, using the left scale and the grid lines that extend out of it, you can easily determine that the value of the last bar is somewhere between 30 and 40.
Note: Scales are not used in Pie graphs.
The first few sections of this chapter will help you conceptually understand how scales and grids work:
The next sections of this chapter deal each type of scale individually:
Finally, the last sections discuss scale and grid features common to all graphs, regardless of the scale types they use:
CORDA