isfinite

Use the isfinite function in APL to check whether a numeric value is finite, meaning it's neither positive infinity, negative infinity, nor NaN (Not a Number). The function returns true for any real number that has a well-defined, bounded value.

isfinite is essential for data quality checks. Division by zero, logarithm of a non-positive number, or other edge cases can produce infinity or NaN in your computed columns. Use isfinite to identify or filter these invalid values before aggregating or visualizing data.

Usage

Syntax

isfinite(x)

Parameters

Returns

true if x is a finite real number (not infinity and not NaN). false otherwise.

Example

Use isfinite to check whether a computed value is finite before using it in aggregations.

Query

['sample-http-logs']
| extend log_duration = log(req_duration_ms)
| extend is_valid = isfinite(log_duration)
| project _time, id, req_duration_ms, log_duration, is_valid

Output

List of related functions

• isinf: Returns true only for infinite values. Use it when you want to distinguish infinity from NaN.
• isnan: Returns true only for NaN values. Use it when you want to detect only Not-a-Number results.
• isint: Returns true for integer values. Use it to check whether a numeric value is an integer rather than a floating-point result.
• log: Returns the natural logarithm. Combine with isfinite to validate log computations on potentially non-positive inputs.
• gamma: Returns the gamma function. Use isfinite to filter out overflow results when computing gamma on large values.

Other query languages