The last column of a gap analysis is used to list the categories that are used to analyze each idea.

1. In the Maps tab, click Run Analysis and select Void Analysis.

   The Void Analysis pane opens.

2. Click Get Started. Optionally, check the Skip this in the future check box to bypass the Get Started pane the next time you perform this workflow.
3. Click Select Analysis Area.

   The Select Analysis Area window opens.

   The analysis area is the area you want to analyze and identify whether voids and gaps are present. You can select multiple sites and neighboring geographies to make up your analysis area.

4. Select sites from the Recent, Currently on map, and From projects tabs and click Apply.

   The specified analysis area is now listed in the Void Analysis pane. By default, a buffer is created around the analysis area and set as the reference area.

5. Optionally, click Change reference area. Select a reference area in the Setting the Reference Area window and click OK.

   Choose from the following options:

   • Expand the analysis area by a factor—The area is expanded by a factor you enter. The default factor is 2. For analysis areas that are point location sites, the radius is multiplied by the factor. For example, a 5-mile ring around a point location is expanded with a 10-mile ring. For analysis areas that are polygons or standard geographies, the area is expanded by the factor size. For example, a polygon expanded by a factor of 2 is expanded with a buffer that increases the area to approximately twice the original size.
   • Expand the analysis area by a fixed distance or time—The area's units (miles, kilometers, or minutes) are expanded by a value you enter. The default is 5.
   • Use the nearest Standard Geography—Use the drop-down menu to select a geography that intersects with the analysis area.
   • Select area manually—Use the Select Reference Area window to choose a second site as the reference area.

6. Click Next.

   Business categories are shown. Business data is used to determine surplus or gaps in the analysis area. You can perform your analysis with a single business (such as Starbucks), a business category (such as Pet Services), or with grouped categories (such as Housing).

7. Select a variable list from the Popular lists or My lists tab. Alternatively, you can click Create Custom List to create a custom list. To view the categories and data source in a list, click Show list
   
   .

   When you select a list, the analysis runs automatically and your results appear in the workflow pane and on the map. For guidance on exploring the analysis results, see Interpret analysis results.

8. Optionally, to export the analysis results, click the Full Results button and then click Export.
   1. Choose Export to Excel or Export to PDF. For Export to PDF, you can include a map of the analysis area, reference area, or both. For both options, you can select the Include individual business locations check box to include locations in the exported results. Including individual business locations in the exported results uses credits.
   2. Click OK. The results are exported in the format you selected.
   • When exporting to PDF, the report includes only locations shown in the current view of the results table. You can export a maximum of 3,000 individual business locations to PDF. If the analysis results contain more than 3,000 locations, the exported locations are scaled down in proportion to the number of results in each category.
   • When exporting to Excel, the report includes locations of all voids, gaps, and surpluses.

9. Click Next.
10. To complete the workflow, the following options are available:
    • View/Export Results—Return to the workflow results.
    • New Void Analysis—Return to the first stage of the workflow to start a new void analysis.
    • I'm Done—Close the Void Analysis workflow.

Style analysis results

In the Void Analysis workflow pane, in the Map style tab, you can customize the appearance of the results on the map.

• By default, nearby point clusters are represented on the map by a single symbol. Uncheck the Cluster points check box to view all the points.
• Expand Analysis area and Reference area to modify the fill and border type, color, and transparency for the areas. You can set different symbols for different business categories on the map.
• Expand Locations only in reference area and Locations in both areas to modify the symbol and its color and size for these locations. Use the All drop-down menu and select a category to create category-specific symbology.

Interpret analysis results

The Void Analysis workflow pane displays the results of the analysis. You can also view more detailed analysis results in the expanded Full Results table and its advanced view.

To filter the results in the workflow pane or results table, click Filter

• Filter by difference type—Check the Show voids only check box to filter the results to voids only.
• Number of results—Select Maximum results per category and enter the number of results to display.
• Filter layer by attributes—Choose an attribute in the Select attribute drop-down menu and specify filter settings. For example, selecting Sales Volume opens a slider showing the minimum and maximum values for sales volume. You can set multiple attribute filters.

Full Results table

In the Void Analysis workflow pane, click Full Results to view an expanded table containing detailed analysis results. You can view the results for individual businesses, or check the Show categories only check box to view the results grouped by category. When checked, the table displays sums of the voids for each category in the analysis area and the locations in the reference area. Click Minimize Table to return to the workflow pane.

By default, values representing voids are indicated by rows shaded red. Click the Table settings button

to change the colors representing gaps, voids, surpluses, and balanced values. If you have selected a normalization variable, you can add density columns to the table by checking the Display density column in advanced view check box.

The Full Results table contains the following information and options:

• Business or category name—You can expand each entry to view additional business and location information. Clicking on a row also expands or collapses the entry.
• Voids in the analysis area—Void symbols indicate a lack of this business in the analysis area. All symbols in this view are voids (Ø Void).
• Closest Location—Distance from the business location in the reference area to the analysis area centroid.
• Locations only in Reference Area—The number of a business locations in the reference area.

Full Results table: Advanced view

The advanced view of the results table provides further details of the analysis results. Use the Advanced view toggle button to open this view. Differences in market size between the analysis and reference areas are displayed under the Normalized Gap and Expected in Analysis Area columns.

Tip:

A normalization variable provides additional context to determine whether a true gap exists, or whether voids are present because the analysis area is smaller or has fewer people than the reference area. For example, the reference area may contain more nail salons than the analysis area, but it may also have a larger population to support them, whereas the analysis area may have fewer people and fewer nail salons, resulting in a Normalized Gap that is less than the Gap.

By default, values representing voids are indicated by rows shaded red. Click the Table settings button

to change the colors representing gaps, voids, surpluses, and balanced values. If you have selected a normalization variable, you can add density columns to the table by checking the Display density column in advanced view check box.

The table is sorted by Gap, from smallest to largest value. Use the arrows next to the column headers to change the sorting order or variable. Click any of the rows in the table to view the associated details. You can view the results for individual businesses, or check the Show categories only check box to view the results grouped by category. When checked, the table displays sums of the gaps for each category in the analysis area and the locations in the reference area.

The advanced view of the Full Results table contains the following information and options:

Use the Normalize results by drop-down menu to change the normalization variable. Select one of the listed variables, or click Browse for a variable to select another variable in the data browser.

Create a custom list

In the Void Analysis workflow, you can create a custom list for your analysis. In step 7 of the workflow above, create your own list by doing the following:

1. Click the Create Custom List button.

   The Create Custom List window opens.

2. In the Use standard data tab, use the Category drop-down menu to choose business categories or click More options and search by NAICS/SIC codes. If you decide to group custom business data, the Void Analysis results will show the total gap or surplus for all businesses, as well as the gap or surplus for each category that you selected.

   See Use a custom layer if you want to bring in data—for example, from a web service—using the From custom layer tab.

3. In the Field to determine void drop-down menu, select the field that will be used to compare the analysis and reference areas.
4. When you are finished selecting categories for the list, you can save the list and run the analysis.
   • Click Run Analysis to immediately run the analysis using the list you made, without saving the list for future use.
   • Click Save List to choose a name and icon for the list. The saved list appears under My lists for future void analyses. When you are finished, click Save and Run Analysis to run the analysis immediately.

Use a custom layer

In the Void Analysis workflow, Esri-provided business data is used to determine the gaps in your analysis area. Alternatively, you can choose a custom layer as the business data. Follow the instructions to add web maps and layers. In step 7 of the workflow above, you can select the layer you added by doing the following:

1. Click the Create Custom List button.

   The Create Custom List window opens.

2. Click the From custom layer tab and then click Add custom layer.

   The Select Custom Layer window opens.

3. Browse to the web map you want to use and expand it to view and select a layer.

   The layer is selected as the business data to be used to determine the gaps in the void analysis. The following drop-down menus are enabled:

   • Field to determine void—The field in the layer used to determine whether the business has a gap or void.
   • Field to group results—The field used to group the results into different categories, similar to categories selected under the By category option.

     If the Field to group results drop-down menu has no selection, the results will be shown as one category—in this case, All.

4. Click Run Analysis.

   The results are displayed in the Results tab of the workflow pane and are also represented on the map.

Set preferences

You can set preferences for Business Analyst Web App in the application preferences. For the Void Analysis workflow, you can turn the intro page on or off, choose your reference area setting, and set your style options. Administrators can set preferences for the entire organization.

To set the workflow preferences, do the following:

1. On the top ribbon, click Preferences
   
   .

   The Preferences window opens.

2. Expand the Maps section, expand the Run Analysis section, and click Void Analysis.
3. You can set the following preferences:

   • Uncheck the Show Void Analysis Intro Page check box to skip the workflow overview page when you run the analysis.

   • For Reference area settings, choose one of the following options:

     • Expand the analysis area by a factor. The default setting.
     • Expand the analysis area by a fixed distance or time.
     • Use the nearest Standard Geography.
     • Select area manually.

   • Expand the Map style section and set the following preferences:

     • Use the drop-down menus to style the symbols for locations only in the reference area and locations in both areas.
     • Set the Fill and Border settings for the analysis area and reference area.
4. To restore the default settings, click Restore Defaults.
5. To save your changes, click Save or, optionally, click Save and Close to close the Preferences window. To view your changes, refresh the app.

Workflow video

This video was created using ArcGIS Business Analyst Web App, where the user experience and workflows are identical to ArcGIS Community Analyst.