CountMatches / List Layer

Count occurrences of a specific value in variable-length lists. Similar to Python's count() method or R's sum(x == value). Returns an integer column with the count of matches in each list. Supports lists of different lengths.

Example transformation:

lists	count_3
[1, 3, 5, 3, 2]	2
[3, 3, 3]	3
[1, 2]	0
[null, 3, null, 3]	2
[]	0

Common applications:

Analyzing keyword frequency in text tokens
Counting error occurrences in log entries
Tracking event repetitions in session data
Measuring symptom frequency in medical records
Detecting pattern frequency in time series
Analyzing user interaction patterns

Note: Lists can have any length, including empty. Type-sensitive comparison. Null values are ignored in counting unless list contains only nulls, then returns null. Empty lists return 0. Particularly useful for analyzing frequency patterns in variable-length data like logs, transactions, or user behaviors.

Table

Select

column

The variable-length list column to analyze. Supports various types:

Numeric lists: [1, 2, 3, 2, 4, 2]
String lists: [red, blue, red, green]
Boolean lists: [true, false, true, true]
Date lists: [2024-01-01, 2024-02-01, 2024-01-01] Lists can have different lengths. Mixed types not supported.

Item

string

The value to count (Item). Must match list element type. Examples:

Numeric: 42 (counts in [42, 1, 42, 3, 42])
String: error (counts in [warning, error, error])
Boolean: true (counts in [true, false, true])
Date: 2024-01-31 (counts in [2024-01-31, 2024-02-01, 2024-01-31])
Time: 15:30:00 (counts in [15:30:00, 09:00:00, 15:30:00])

AsColumn

name

Name for the new column. If not provided, the system generates a unique name. If AsColumn matches an existing column, the existing column is replaced. The name should follow valid column naming conventions.