Multi-Field Sort Keys For Custom Numbering In Arcmap

The Problem with Default Numbering in ArcMap

ArcMap’s default numbering tools, while useful, lack flexibility for more complex sorting needs. The standard numbering functionality relies on sorting records by a single field, typically a primary key or object ID field. This works well for basic sequencing, but fails to meet specialized requirements.

For example, default numbering cannot easily handle situations where records need to be sorted by multiple fields or attributes prior to assigning numbers. A common case is wanting to numerically sort features within groups based on category, location, or other fields. The default tools do not provide options for concatenating fields together into a single sort key.

Without support for multi-level and multi-field sorting, organizations often have to rely on error-prone and time-consuming manual methods to achieve specialized numbering sequences. Customized sorting is critical in real-world mapping workflows to assign codes by geography, chronology, taxonomy, or other domains.

Understanding Multi-Field Sort Keys

Multi-field sort keys provide a flexible syntax for precisely controlling the sort order of records by allowing multiple fields to be concatenated into a single string value. This value, referred to as the sort key, instructs ArcMap how to numerically or alphabetically sequence rows before labeling or symbolizing.

The basic syntax combines field names and optional separators or processing functions using brackets and quotes. For example: [Field1] & “_” & [Field2] would yield values like “Value1_Value2”. The components are combined left to right to form the final sort key value.

Any fields from the attribute table can be referenced, including numeric and text fields. Custom expressions and formulas are also supported for advanced usage. Sort keys can leverage multiple nested functions to manipulate text case, formatting, and field concatenation.

By leveraging several chained keys, it is possible to sequentially sort by major categories, subsequences, and tertiary attributes. For example, features could be sorted by region, then year, then size. This allows numbers to be assigned that uniquely identify nested groups in a customized, meaningful order.

Step-by-Step Guide: Configuring Multi-Field Sort Keys

The steps to configure a multi-field sort key are:

1. In ArcMap, open the layer’s attribute table that you want to customize numbering for.
2. Right-click on the primary key field and select Properties.
3. In the Field Properties dialog, switch to the Advanced tab.
4. Click the button next to the Sort Key box to open the Symbol Value Field dialog.
5. In the Sort Key box, enter the concatenation and processing logic for the desired multi-field key.
6. Use field names enclosed in brackets along with any text or functions.
7. The sort key segments will combine left to right to form the final value.
8. After entering the formula, click OK on each dialog to save the configuration.

Now when the layer is rendered or labeled, the features will sort in the defined sequence. Numbers and symbols can then be assigned based on the customized sort order.

For example, a two-level key like [Region] & ” ” & [ID] would sort first by the text Region field, then secondarily by the ID field. This allows numbered labels to be assigned sequentially within groups.

Custom Formatting with VBScript and Python

For advanced numbering capabilities, the scripting languages internal to ArcMap can be utilized to fully customize and automate numbering. VBScript and Python can query field values, update attributes on-the-fly, and integrate with models or tools.

Common uses cases include:

• Lookups to assign codes from separate tables
• Advanced string processing or regular expressions
• Repeated field analysis to find minimum available IDs
• Generation of checksums or hash values
• Data validation to enforce business rules

The scripts have access to the full range of ArcObjects, so the attribute table can be processed record-by-record to generate any numbering sequence. The results can be written back to attributes or label fields for cartographic display.

Automating these actions eliminates the manual work of updating values and ensures consistency. Custom scripts can also be bundled into tools, models or add-ins for re-use across multiple datasets.

Troubleshooting Common Issues

When working with advanced sort keys, there are a few common errors and issues to be aware of:

• Invalid key syntax – A formula might reference fields that do not exist or use unsupported logic, functions or variables. Carefully check for errors with brackets, punctuation etc.
• Previews not updating – The map display may fail to reflect changes after editing sort keys, requiring a refresh.
• Export failures – Complex attributes can sometimes cause crashes or hangs when exporting maps or tables. Simplify logic where possible.
• Performance delays– Sorting and rendering tens of thousands of complex records can impact responsiveness. Filtering records may help narrow focus.

Testing scripts on small samples first is advisable to catch syntax issues early. Previewing a map after changes confirms numbering behaves as expected before full exports.

Example Multi-Field Sort Keys

Below are examples of common multi-field sort keys:

[Category] & Right("0000" & [Seq_ID],4) 

Result: Sorts by text category, then assigns 4-digit numeric codes sequenced within each group.

************************

[Region] & [Year] & LPad([Site_ID],3,"0")

Results: Sorts by region text, then year number, then 3-character, zero-padded site code. Unique ID formed by concatenating fields.

************************ 
  
[Type] & [Floor] & [Room]

Results: Assigns sequentially numbered rooms first by building type, then floor number, then room order per floor.

These samples demonstrate how multiple fields can be integrated to precisely sort records for customized numbering and symbolization.

Text, numbers, padding functions, and multiple attributes can be combined to suite specific use cases. The full flexibility of scripts can also be utilized for advanced operations.

Following core best practices of nesting sort tiers from major to minor and validating field names will help craft reliable sort keys for complex datasets.