Displaying symbols on a map

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1. Overview

A symbol is a type of map element that is used to represent location points on a map. These can be added to your map from map resources, or from coordinates in your data source.

Using size rules, the sizes of symbols can be varied according their data values like bubbles. For example, in a proportional symbol map, each symbol indicates the location of a city, and the size of the symbol represents a range of corresponding sales figures (or other measure values).

Additionally, using color rules, the color of each symbol can be varied according to data values.

The following walkthrough shows you how to create a proportional symbol map in which the location of the symbols comes from the data and both the size and color of each symbol varies according to data values.

2. Prepare location and measure data

Consider the following example, which specifies the decimal longitude and latitude for various cities in Canada. These values will be used to create and position symbols on the map. There is also some measure data, such as population and sales figures for each city.

Excel spreadsheet with location and measure data
Excel spreadsheet with location and measure data

3. Add a map visualization

Create a new dashboard based on the Blank template. Go to the toolbar, click Data Visualization, and then click Map. An empty map visualization is added to the canvas.

In our example, we can choose to display a particular map resource under the symbols for context instead of allowing the map to look for resources that match our data.

Select the map visualization and click Properties. Scroll down and look for the Show Only Requested Maps checkbox. Enable this option to turn off the automatic map loading behavior and make it so that only map resources you specifically drag from Explore are displayed.

Show Only Requested Maps property
Show Only Requested Maps property

Go to the Explore panel and expand the Maps \ Shared \ States and Provinces folder.

Drag the Canada (States and Provinces) map onto the empty map visualization. This is one of the built-in map resources included with Dundas BI.

Drag a map resource
Drag a map resource

You won't be able to see the map because data has not been added yet, but the map resources will be indicated in the Main properties, under Requested Maps.

4. Add data to the map

In our example, we have imported our Excel data, and will drag the CityName column under its data connector in the Explore window onto the map visualization. You should now be able to see the map of Canada, except that the shapes appear in the top left corner. To zoom in, switch to View mode in the toolbar, zoom in, and switch back to Edit mode.

Pan and zoom the map in View mode
Pan and zoom the map in View mode

We can drag the Population and Sales columns onto the map. These will be added as measures, as shown in the Data Analysis Panel. Edit the Population measure and change its Format to N0.

Drag CityName column to map
Drag CityName column to map

The map does not display any symbols yet because they will be generated dynamically from location data.

5. Connect symbol location to data

Open the Data Analysis Panel for the map and click Visualization in order to modify the visualization connections.

Scroll down to find Longitude (X) and Latitude (Y) under Symbols.

Drag from the Explore window or click to add the longitude and latitude coordinates.

Symbols for each city are now displayed on the map.

Add Longitude and Latitude connections
Add Longitude and Latitude connections

If you switch to View mode you can access a tooltip on each city that shows its name, population, and sales figure.

Symbol tooltip
Symbol tooltip

You can configure the symbol tooltip from the Visualization tab or from the map's Text properties.

6. Symbol color rules

The symbols on the map have different colors because of a symbol color rule, which was added automatically and corresponds to the first measure, Population.

Symbol color rule
Symbol color rule

Click Auto Color Rule to make adjustments to the From Color or To Color. You can also change the Number of Classes (i.e. number of data ranges) that are generated and the Distribution method which determines how data points (i.e. symbols) are slotted into the various classes.

Symbol color rule properties
Symbol color rule properties

6.1. Distribution methods

The default distribution method is Round Interval, which divides the entire data range into equally spaced intervals using rounded values. Similarly, the Equal Interval distribution method divides the entire data range into equally spaced intervals but does not round the values.

These methods may not be the best option when your data is distributed unevenly, because the data points might be slotted into a single or very small number of intervals. The Equal Distribution method fits such situations better, as it divides the entire data range into intervals containing the same number of data points.

The Continuous distribution method maps the entire data range to a continuous range of colours, so that each distinct value has its own corresponding color between the two set colors.

7. Connect symbol size to data

Open the Data Analysis Panel for the map and click Visualization in order to modify the visualization connections.

Scroll down to find the Size under Symbols. Use Click to add to connect to the Sales measure.

The sizes of the symbols now vary according to sales figures for each city. Similar to color rules, a size rule has been automatically generated. You can modify this rule in the same way as color rules, except that instead of a range of colors, you set a range of sizes.

Symbol size rule properties
Symbol size rule properties

8. Add paths between the symbols

If your data contains pairs of symbol names, you can assign these to the map to display a link between symbols, similar to a relationship diagram.

Open the Visualization tab of the Data Analysis Panel for the map and expand the Paths section.

Add a hierarchy with names matching symbols under Symbol Link Start Name . Edit the hierarchy to set Shown Totals to No Totals to remove rows of data that omit the hierarchy's values.

Add another hierarchy containing symbol names under Symbol Link End Name.

Similar to the symbols, a color rule has been automatically generated and corresponds to the first measure, Population, and a size rule can be added.

Link the symbols
Link the symbols

9. Add a legend

Both symbol color rules and symbol size rules have a Display In Legend property which is enabled by default. Simply add a legend to the canvas from the Data Visualization toolbar and connect it to the existing map. The legend will automatically display items corresponding to the different color and size data ranges.

Legend items generated from symbol color and size rules
Legend items generated from symbol color and size rules

10. Show heat maps

Important
Enabling heat maps overrides symbol settings, such as Color, Size, Tooltip, and symbol interactions.

To replace the existing symbols with heat maps, drag the Sales measure to Heat map in the Data Analysis Panel.

Heat maps replace the existing symbols
Heat maps replace the existing symbols

Open the Look properties for the map and click Heat Map Style under the Appearance section.

Click Heat Map Style
Click Heat Map Style

Increase the Point Radius and Blur Radius values, and set the Minimum Opacity to 70%.

Heat maps start merging when their areas overlap
Heat maps start merging when their areas overlap

11. Notes

11.1. Loading map content automatically

By default, the Show Only Requested Maps property is turned off for a map visualization, which means the map will load content from built-in map resources automatically when there is a match with the metric set data added to the map.

For example, add a blank map visualization to the canvas and then drag like our example above onto the map. In our case, the map visualization will automatically load a built-in map resource containing symbols with names matching the CityName column. The viewport of the map will also be adjusted automatically to center upon the matching symbols.

Symbols are automatically loaded after adding Excel data to the map
Symbols are automatically loaded after adding Excel data to the map

Symbols that do not match the data will appear with a grey, semi-transparent color, unlike the symbols with matching data that have a color rule applied. The default symbol appearance can be customized in the map's Look properties.

12. See also

 

Dundas Data Visualization, Inc.
500-250 Ferrand Drive
Toronto, ON, Canada
M3C 3G8

North America: 1.800.463.1492
International: 1.416.467.5100

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