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.

Using size rules, the size of a symbol can be varied according to corresponding data values. 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 Excel spreadsheet, 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. In addition, the spreadsheet contains 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

Create a data connector in Dundas BI by dragging this spreadsheet from Windows Explorer to the Dundas BI Explore panel.

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.

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

4. Add a map resource

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.

5. Add data to the map

Locate and expand the Excel data connector in Explore. Drag the CityName column 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. The reason for this is that the viewport of the map is configured by default to display the world map. You will need to switch to View mode to pan and zoom-in as needed (for example, by using the mouse wheel). Switch back to Edit mode when done.

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

Next, 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

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

5.1. Symbol Compatible Name

The following is a side-topic which is not part of the walkthrough.

If you click Visualization in the Data Analysis Panel, you'll see that the SYMBOL NAME field is connected to the CityName column from the Excel data. This connection is necessary for matching symbols with your data.

Symbol name is connected to the CityName column
Symbol name is connected to the CityName column

If you're using pre-defined symbols from a map resource (instead of generating them from location data), you need to make sure the names of the symbols can be matched with the data values. Otherwise, you must change the connected data or give each symbol element a Symbol Compatible Name to facilitate connection to data.

For example, your CityName data has a New York City entry but in your map resource the symbol is named New York instead. Matching will fail in this case. To fix the connection, edit the properties of this map symbol in Dundas BI and set the Symbol Compatible Name property to New York City. This needs to be done for each symbol element that fails to match.

Symbol Compatible Name property for a map symbol
Symbol Compatible Name property for a map symbol

6. 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 the LONGITUDE (X) and LATITUDE (Y) fields under Symbols.

Go to your Excel data connector in the Explore panel and drag the Longitude column onto the LONGITUDE (X) field. Similarly, drag the Latitude column onto the LATITUDE (Y) field.

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.

7. 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

7.1. 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 the color range in a continuous fashion.

8. 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 field under Symbol. 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

9. Add paths between the symbols

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

Add the SoldFrom hierarchy to the Symbol Link Start Name field. Edit the hierarchy to and set Shown totals to No Totals.

Add the CityName hierarchy to the Symbol Link End Name field.

All the target cities are now connected to the source city (Toronto). 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.

Connect the symbols
Connect the symbols

10. 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

11. 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 the Heat map field 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

12. Notes

12.1. 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 the CityData Excel spreadsheet (Sheet1) onto the map. 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 that do not match the data may still be loaded but these will appear with a grey, semi-transparent color. The use of semi-transparency allows overlapping symbols to be detected. Symbols connected to data will be displayed with color due to the symbol color rule which is also added.

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

13. See also

 

Dundas Data Visualization, Inc.
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