Table Manipulation

group-by

Group a table of transactions by a key function. This is one of the most powerful functions for analysis.

Syntax:

(group-by table key-fn)

Parameters:

• table: The list of transactions
• key-fn: A lambda function that extracts the grouping key from each transaction

Returns: A list of groups, where each group is:

("GroupName" (transaction1) (transaction2) ...)

Examples:

Group by Category

kakei transform --program "(group-by table (lambda (pair) (cdr (assoc 'category (cdr pair)))))"

Output structure:

(("Food" 
  (ID-001 . ((date . "2025-01-01") (amount . -1000) ...)))
 ("Transport"
  (ID-002 . ((date . "2025-01-02") (amount . -2000) ...)))
 ("Salary"
  (ID-003 . ((date . "2025-01-15") (amount . 50000) ...))))

Group by Account

kakei transform --program "(group-by table (lambda (pair) (cdr (assoc 'account (cdr pair)))))"

Group by Date

kakei transform --program "(group-by table (lambda (pair) (cdr (assoc 'date (cdr pair)))))"

How it Works:

For each transaction in the table:

1. The lambda function extracts a grouping key (e.g., category name)
2. Transactions with the same key are grouped together
3. The result is a list of groups labeled by their key