Mapping Tutorial: Thematic Analysis
Selecting Indicators for Mapping
The Special Needs Populations Mapping Tool can map a number of variables which are grouped by 6 populations (Geoclip refers to these populations as themes). The 6 special needs populations are:
- Disabled
- Frail Elderly
- Children
- Racial/ethnic minorities
- Limited English
- Resource Poor
There are two ways to display special needs populations on the map using the Indicator Selector shown in the Figure below.
- Use the upper set of pull-down menus to select a population (theme) and variable to display the data as shaded geographic areas with the shading intensity corresponding to the values in the displayed legend. This approach is called shaded (polygonal) analysis. Shaded analysis is used for relative quantity indicators (percentages, growth rates, averages).
- Use the bottom set of pull-down menus to select a second population and variable to display the data as proportional symbols (e.g., circles) with the area of the symbol corresponding to the size of the indicator. Analysis by proportional symbols displays absolute quantities (numbers, areas) in the foreground. In this case, the Key shows how the circle areas correspond with the value displayed.
Indicator Selector with sample indicators chosen
Provides access to Additional Information and documentation about the chosen indicator. From this box, you can export the value of the indicator into a spreadsheet for all geographic units on the map.
Opens the Configure Indicator panel for adjusting the analysis parameters of the indicator. This panel is specific to the type of analysis chosen and is further described below in the Symbols Analysis section.
Note: to change the type, size, and color of the symbol used for the symbol analysis, you must first select a secondary population and theme for that population, and then click the Configure Indicator button.
Information about the data source and the value of the indicator for the reference territory (USA) are shown at the bottom of the Key.
Once an indicator has been chosen, the map refreshes and the corresponding Key is displayed automatically.
Shaded Analysis
Shaded analysis (or polygonal analysis) is used for relative value indicators (percentages, growth rates, averages).
For shaded analysis, the Key shows the colors and thresholds for each group. If the indicator is not available for a geographic unit (value missing, secret statistic or division by zero), it will appear in grey (N/A in the Key). The number of geographic units in each group is shown in brackets.
Information about the data source and the value of the indicator for the reference territory are shown at the bottom of the Key.
You can click on any of the colored blocks in the Key; on the map, this temporarily hides all the geographic units belonging to other categories.
Provides access to a panel providing Information About the Indicator. From this panel, you can export the value of the chosen indicator into a spreadsheet, for all the geographic units on the map.
Opens the Configure Indicator panel for adjusting the analysis parameters.
Modifying Parameters
You can modify the following parameters:
- the number of ranges, from 3 to 8
- the color palette, for color-coding the ranges
- the sorting method.
Sorting methods: the following methods are available: manual, quantiles (equal count), Jenks automated distribution method and discretizations calculated using standard deviations. In manual discretization mode, range thresholds can to be defined in the text fields or by adjusting the cursors by click-dragging the mouse, on the diagram at the bottom of the panel.
Hide features' stroke: When this box is ticked, the boundaries between the geographic units are hidden.
Continuous tinting: When this box is ticked, coloring of the geographic unit is done on a continuous basis (instead of having different colors for each range).
Validates the parameters selected and closes the panel.
There are two bar charts in the analysis parameters panel: a frequency bar chart and a distribution bar chart.
Frequency: this bar chart displays the geographic units as Northing (Y) and the indicator value as Easting (X). Moving the mouse over the bar chart reveals the geographic units on the map (as red circles).
Distribution: this bar chart displays the indicator value as Easting (X) and the number of geographic units as Northing (Y). Thus the bar chart displays the type of distribution for the indicator (normal, asymmetrical, etc.) in visual form. The curve shows the same data after smoothing.
Symbols Analysis
Analysis by proportional symbols displays absolute quantities (numbers, areas) in the foreground. In this case, the Key shows how the circle areas correspond to the value displayed.
opens the following panel for adjusting the analysis parameters. Several features are offered on this panel.
Symbol: chooses to choose the type of symbol.
is used to change the fill color for the circles.
Opacity: sets the opacity of the color.
Fill Type: displays a view with solid disks or a view with line circles.
buttons increase or decrease the size of the circles while keeping them in proportion. The Key values are adjusted automatically.
Lock correspondence: maintains the correspondence between the circle size and the indicator value, for several successive analyses, in order to be able to compare a series of maps.
Display values: displays the value of each circle. For the purposes of readability, the labels are only visible when the zoom level passes a certain threshold.
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