Modify Dot Density Thematic Map

Instructions for use

You can modify various parameters of the dot density thematic map in the "Dot Density Thematic Map" window to achieve a more suitable thematic map effect.

Operating Steps

  1. In the layer manager, select a dot density thematic map layer, click the pop-up group dialog button at the bottom right of the "Dot Density" group. The "Dot Density Thematic Map" window displays the settings information of the selected dot density thematic map.
  2. Thematic Map Layer: Displays the name of the currently displayed thematic map.
  3. Expression: Displays and sets the thematic variable used to create the current dot density thematic map, which is a single property field or a mathematical expression of fields.
    • Click the drop-down button of the "Expression:" combo box. The drop-down list displays all property fields of the region dataset used to create the current dot density thematic map.
    • In the drop-down list, select the thematic variable (a single property field) for the current dot density thematic map layer. You can also click "Expression..." in the drop-down list to open the "SQL Expression" dialog and construct a field expression as the thematic variable for the dot density thematic map.
    • The current dot density thematic map will immediately re-render based on the modified thematic variable and refresh the display effects.

    Note: 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 operation expression, such as (SmID) or (SmID + 1). Currently, conditional expressions are not supported for setting thematic map fields. If the field expression is a conditional expression, such as "SmID > 100", the thematic map creation will fail, and the output window will display "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 of a region. In a dot density thematic map, if one dot represents a certain value, the number of dots in a region multiplied by the value per dot equals the thematic value for that region. Here, use the "Value Represented by a Single Dot:" numeric display box to set the value that a single dot represents in the dot density thematic map.
    • You can enter a value in the text box to the right of this label control or use the up/down spin buttons in 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, then for a region with a 1994 population of 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 sets the number of dots contained in the region with the maximum thematic value expressed by dot density. This parameter can be used to determine the density of dot distribution on the map.
    • You can enter a value in the text box to the right of this label control or use the up/down spin buttons in the text box to adjust the data. The number of dots for the maximum value changes inversely with the value represented by a single dot: a higher value per dot 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. You can also adjust these two parameters based on the dot density distribution on the thematic map.
  6. Point Style: You can set the point style for all dots in a dot density thematic map.
    • Click the button to the right of the "Point Style:" label control to open the "Styles" window (for specific operations, refer to: "Point Symbol Style Settings" window) and configure 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 what-you-see-is-what-you-get effect. You can also disable real-time refresh by unchecking the "Enable Instant Refresh" checkbox at the bottom of the dialog. If "Enable Instant Refresh" is unchecked, after completing all parameters, click the "Apply" button at the bottom of the dialog to apply the parameters to the current thematic map.
Important 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, you can directly select a saved template from the drop-down menu of the "Template" drop-down button and apply it to the creation of other thematic maps.

Related Topics

Create a New Dot Density Thematic Map