List.Outliers

Identifies outliers in a list of numerical values using the Interquartile Range (IQR) method.

Syntax

List.Outliers(
    values as list,
    optional multiplier as number
) as list

Parameters

• values: A list of numerical values to analyze for outliers.
• multiplier (optional): A number to adjust the IQR threshold for defining outliers. Default is 1.5.

Return Value

Returns a list of outlier values identified in the input list based on the IQR method. If no outliers are found, the function returns an empty list.

Remarks

• The function first removes nulls, empty strings, and whitespace entries, then selects only valid numeric values.
• Outliers are defined as values below $Q_{1} - 1.5 \cdot IQR$ or above $Q_{3} + 1.5 \cdot IQR$, where $Q_1$ and $Q_3$ are the first and third quartiles respectively.

Examples

Example 1: Returns outliers from a list with extreme values.

List.Outliers({1, 2, 3, 4, 5, 6, 50, 100})

Result

{50, 100}

Example 2: With a higher multiplier, identifying outliers becomes stricter.

List.Outliers({1, 2, 3, 4, 5, 6, 50, 100}, 3)

Result

{100}

Example 3: Returns an empty list if there's no outlier.

List.Outliers({10, 12, 14, 15, 16, 18, 20})

Result

{}

Example 4: Ignores nulls and empty strings.

List.Outliers({1, null, "", 2, 3, 4, 5, null, 6, 50, 100})

Result

{50, 100}