The array_iff function in Axiom Processing Language (APL) allows you to create arrays based on a condition. It returns an array with elements from two specified arrays, choosing each element from the first array when a condition is met and from the second array otherwise. This function is useful for scenarios where you need to evaluate a series of conditions across multiple datasets, especially in log analysis, trace data, and other applications requiring conditional element selection within arrays.

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For users of other query languages

If you come from other query languages, this section explains how to adjust your existing queries to achieve the same results in APL.

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Usage

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Syntax

array_iff(condition_array, array1, array2)

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Parameters

  • condition_array: An array of boolean values, where each element determines whether to choose the corresponding element from array1 or array2.
  • array1: The array to select elements from when the corresponding condition_array element is true.
  • array2: The array to select elements from when the corresponding condition_array element is false.

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Returns

An array where each element is selected from array1 if the corresponding condition_array element is true, and from array2 otherwise.

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Use case examples

The array_iff function can help filter log data conditionally, such as choosing specific durations based on HTTP status codes.Query
['sample-http-logs']
| order by _time desc
| limit 1000
| summarize is_ok = make_list(status == '200'), request_duration = make_list(req_duration_ms)
| project ok_request_duration = array_iff(is_ok, request_duration, 0)
Run in PlaygroundOutput
ok_request_duration
[0.3150485097707766, 0, 0.21691408087847264, 0, 0.2757618582190533]
This example filters the req_duration_ms field to include only durations for the most recent 1,000 requests with status 200, replacing others with 0.