Thematic Mapping Capabilities

Background themes are displayed on layers or region objects to show some data classification, either with ranges or discrete values.

In CartoVista, this type of thematic map is typically used as a background theme on layers containing region objects. If you have numerical data that links to geographic regions, this type of thematic map, also known as a choropleth map will help you understand and compare your values by displaying color ranges. When you select an indicator from the background theme tab, CartoVista reads your data values and calculates appropriate ranges automatically. CartoVista uses the quantile classification method to create the range thresholds.

Once the range theme is displayed you can then use the thematic settings dialog to customize the display. With the different options you can:

• Choose the number of ranges.
• Change each range thresholds by typing a number in the text box.
• Use the histogram / graph window to visually change the range thresholds based on inflection points in your data set.
• Choose a color scheme for the range map or specify colors individually.
• Reverse the colors.

If your data contains discrete values such as a classification or category, you can use an individual values theme to represent each value with a color. Individual values theme are usually constructed from indicator data stored as strings (characters). For example, this type of theme is very useful to show a land use classification by color for different regions (commercial, residential).

Once the theme is displayed, the thematic settings dialog is accessible to customize the settings and change the color for each individual value in the theme.

Foreground themes are displayed on top of the map to add another dimension to the background theme. Using symbols and pie charts, you can show and easily compare numerical values in your data.

In CartoVista, symbolic themes are available in the foreground theme tab. Symbolic themes can use a combination of graduated symbols, symbol type (shape) and color to represent indicator values on your map. In CartoVista, this multiple thematic representation is called a multi-variate symbolic theme.

Symbolic themes can be applied to all layer types, whether they contain region, polyline or point objects. When working with regions or lines, the actual symbol point is displayed at the centroid of each object.

A symbolic theme with symbol color is used to show an indicator numeric values with continuous colors. The minimum and maximum values of the chosen indicator are associated with different colors. These two colors are used to create a gradient that includes a representation of the intermediate values.

To create a symbolic theme by color, click on the show using symbol color button.

In statistical analysis, pie charts are useful to compare values for different categories of information. The area of each sector in a pie chart indicates the category's relative importance in relation to others. For example, in the context of an election, you may create a pie chart map that outlines each political party with a specific color to compare the number of votes and understand its geographic distribution.

In CartoVista, pie charts are displayed as a foreground theme, which can be based on any type of layer (regions, lines or points). When displaying a pie chart theme on a layer of regions or line objects, the pies are created at the centroid of each object.

A pie chart is constructed from a collection of indicators, which have to be of the same data unit. To create a pie chart theme, select the foreground theme tab and simply select the indicators you wish to use from the list. You can then change the colors assigned to all values using the thematic settings dialog.