Fuzzy Logic

Arc-SDM uses a fuzzy logic "calculator" to combine evidential themes using the fuzzy operators described in the section discussing the fuzzy logic method (fl1.pdf). Each of the "calculations" or operations is recorded in a dBase file that then can be viewed, rerun and/or plotted at any point in time.

To combine two or more themes using a fuzzy operator:

Select 'Fuzzy Logic...' from the SDM menu.

You are first prompted to select an existing fuzzy logic model file (.dbf).

To...

  
...append a record of the operations to be done in this session to an existintg file (created during a previous session): select the file and click 'OK'.
...create a new file:
  1. Click 'Cancel'.
  2. When prompted, specify a name and location for the new fuzzy logic model file. The default name is flmdl<#>.dbf.

Then the "fuzzy logic calculator" dialog is displayed:

The listbox contains all of the theme-field pairs from the active view for which the values in the field or grid cells falls in the range [0,1]. In the case of a floating point grid theme, the "field" is identified as 'Value'.

  1. Select two or more evidential themes to combine:

    Select a theme-field pair by clicking it in the listbox display.
    Select one or more additional theme-field pairs by holding down the shift-key and clicking them. NOTE: Two fields from the same theme attribute table cannot be selected at the same time.
    When two or more theme-field pairs are selected, the 'Calculate' button becomes active.

  2. Select a fuzzy operator to use to combine the themes.
  3. Click 'Calculate'.
  4. If the GAMMA operator is selected, you will be prompted to specify a fuzzy gamma operator after you click 'Calculate'.
  5. When prompted, specify a name and location for the output theme. The default names are as follows:

The default filename for the output grid from a fuzzy ...

 ... operation is ...
AND And<#>
OR Or<#>
SUM Sum<#>
PRODUCT Prd<#>
GAMMA Gamma<#>

The new theme will be added to the active view and to the top of the theme-field list in the dialog box for input to a subsequent operation.

To view the contents of the fuzzy logic model

  1. Click 'View Model (Text)'.

This displays the contents of the file as in the following example:

NOTE: The functions run from the 'Plot' and 'Run' buttons are described in the next section, 'Process Existing Model'.

To Select another model file

At any point you can click the button labelled 'Select Model File...' to select another file. Subsequent operations will be appended to the newly selected file until the dialog is closed or another file is selected.

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