Ranged Map Type
The Ranged map type splits the numerical data into groups of values. Each group has a beginning and ending value and is represented by a specific color. Figure 14-5 is an example of a Ranged map showing the sales by US city.
Figure 14-5. Range map showing sales by US city.
The legend in the top right hand corner shows the range of values displayed and which colors map to each range. In parentheses, it also tells you how many locations fall within that range. For example, there are twelve states that have sales between $74,000 and $388,000.
Ranged map types have different options for calculating the beginning and end point of each range. When you select the Ranged type in the Map Expert, the bottom section changes so that you can set these options. Figure 14-6 shows how this looks.
Figure 14-6. Ranged map type options.
The first and second options, Number of Intervals and Distribution Method, work together. The first option determines how many intervals to use. If you have a large number of areas getting mapped, increasing the number of intervals makes it easier to differentiate between the groups. The second option, Distribution Method, determines how the range of values is calculated. You can choose between Equal Count, Equal Range, Natural Break, and Standard Deviation.
The Equal Count option sets the range so that each group has an equal number of areas that it accounts for. The option Equal Ranges looks at the overall range of values to choose and breaks them up mathematically. Thus, each range spans the same number of data points. The option Natural Break calculates the average value for each range and tries to minimize the differences between them. The option Standard Deviation assigns intervals in such a way that the middle interval breaks at the mean (or average) of the data values and the intervals above and below the middle range are one standard deviation above or below the mean.
The remaining options let you choose the range of colors displayed on the map as well as whether to display intervals that don’t have any data points to map.
