Modify Dot Density Thematic Map

Feature Description

In the "Dot Density Thematic Map" window, you can modify various parameters of the Dot Density Thematic Map to achieve a more suitable cartographic effect.

Operation Steps

  1. In the layer manager, select a Dot Density Thematic Map layer. Click the popup group dialog button at the bottom right corner of the "Dot Density" group. The popped-up "Dot Density Thematic Map" window displays the setting information of the selected Dot Density Thematic Map.
  2. Thematic Map Layer: Displays the name of the currently presented thematic map.
  3. Expression: Displays and sets the thematic variable used to create the current Dot Density Thematic Map, which can be a single property field or a mathematical expression of fields.
    • Click the drop-down button of the "Expression:" combo box. The dropdown list shows all property fields of the region dataset used to create the current Dot Density Thematic Map. Fields in this list are displayed as Field Alias by default. If necessary, you can switch to field names in the File tab -> Options group. For details, refer to the Preference Settings document.
    • In the dropdown list, select the thematic variable (a single property field) for the current Dot Density Thematic Map layer. Alternatively, users can click the "Expression..." item in the dropdown list and build a field expression in the popped-up "SQL Expression" dialog box to serve as the thematic variable for the Dot Density Thematic Map.
    • The current Dot Density Thematic Map will immediately re-map based on the modified thematic variable and refresh the display effect.

    Notice: When creating a thematic map for data with Oracle Plus or SQL Plus engine types, the field expression can only be a field value or a field arithmetic expression, such as (SmID) or (SmID + 1). Conditional expressions are currently not supported for setting thematic map fields. If the set field expression is a conditional expression, e.g., "SmID > 100", the created thematic map will fail, and the output window will prompt "Thematic map update failed".

  4. Value Represented by a Single Dot: The number or density of dots in a Dot Density Thematic Map reflects the thematic value corresponding to an area. In a Dot Density Thematic Map, a single dot represents a certain value. Therefore, the number of dots in an area multiplied by the value represented by each dot equals the thematic value for that area. Here, use the "Value Represented by a Single Dot:" numeric display box to set the numerical value expressed by a single dot in the Dot Density Thematic Map.
    • Users can input a value in the text box on the right side of this label control or use the up/down spinner buttons within the text box to adjust the data. As shown in the figure above, if the value entered in the text box to the right of "Value Represented by a Single Dot:" is 500,000, and the 1994 population for a region is 1,000,000, the number of dots distributed in that region will be 10.
  5. Number of Dots for Maximum Value: The "Dots for Max Value:" numeric display box is used to set the number of dots contained in the area with the maximum thematic value expressed by dot density. This parameter can be used to determine the density of dot distribution on the map.
    • Users can input a value in the text box on the right side of this label control or use the up/down spinner buttons within the text box to adjust the data. The number of dots for the maximum value is negatively correlated with the value represented by a single dot: a larger single dot value results in fewer dots for the maximum value, and vice versa. After setting either parameter, the system automatically calculates the value of the other parameter. Users can also adjust these two parameter values based on the distribution of dot density on the thematic map.
  6. Dot Style: Users can set the dot style for all dots in a Dot Density Thematic Map.
    • Click the button on the right side of the "Point Style:" label control. In the popped-up "Styles" window (for specific operations, refer to: "Point Symbol Style Settings" Window), set the style for the current Dot Density Thematic Map.
  7. All parameters in the "Dot Density Thematic Map" window are immediately reflected in the corresponding thematic map layer in the current map, achieving a WYSIWYG (What You See Is What You Get) effect. Users can also disable real-time refresh by unchecking the "Enable Instant Refresh" checkbox at the bottom of the dialog box. If the "Enable Instant Refresh" checkbox is not checked, after completing the parameter settings, users can click the "Apply" button at the bottom of the dialog box to apply the dialog box parameters to the current thematic map.
Notes:
  • Both created and modified Dot Density Thematic Maps can be saved as templates for application in thematic map creation for other layers. For details on saving as a thematic map template, refer to: Save to Thematic Map Template Library.
  • When creating a thematic map using the template method, users can directly select a saved template from the dropdown menu of the "Template" drop-down button to apply it to the creation of other thematic maps.

Related Topics

Create a New Dot Density Thematic Map