Reading maps displaying data can be a little overwhelming, especially if you don’t have any experience. This article will help break down how to read a single indicator map and a bivariate map using the legend. Knowing how to read the legend can help you uncover more patterns in the data you might have overlooked.
Table of Contents
Reading a map legend
Seek’s maps use a color ramp to visualize data in your selected geographies. The legend shows all of the colors which might be shown on the map. Each geography within your selection is assigned a color based on the groups defined in the legend.
Single variable map legend
Figure 1. An example of a single variable map legend showing Median Household Income.
A single indicator map in Seek breaks the range of values into groupings using the natural breaks methodology. Read more about how legend groupings are created.
The single indicator legend displays the lowest value for each group at the top. In the above pictured example (figure 1), the first group has a minimum value of $32,132. The second group has a minimum value of $44,717. This means the first group has a range of $32,132 – $44,716.
The first group always contains the lowest value, while the last group always contains the largest value.
The last group has a minimum value of $75,596 and a maximum value of the highest value in the whole selection. (This upper limit is not currently listed on the map, but could be found on the table view.)
Bivariate map legend
Figure 2. An example of a bivariate map legend showing Median Household Income (variable A), and Income Inequality (variable B).
A bivariate map shows two indicators at a time instead of one. The legend is similar to the single indicator legend, but uses a diverging color scale. Seek provides a yellow – blue scale or a magenta – green scale.
The geographies are classified into 3 groups for each indicator with a low, middle, and high. The relationship between the two indicators results in a total of nine color groups, as shown below (fig. 3 & 4).
Figure 3. A diagram labeling the axes of a bivariate legend which show the intersection of groupings for variables A & B as nine different colors.
Figure 4. A diagram listing each of the nine colors positions from a bivariate legend and the relationship to the groupings for variables A & B.
If variable A represents Median Household Income, and variable B represents Income Inequality:
Geographies colored with lightest lightest gray (group 1) represent places which have a low Median Household Income (variable A) and low Income Inequality (variable B).
Geographies colored with a dark blue (group 8) represent places with a middle Median Household Income and high Income Inequality.