The array_index_of function in APL returns the zero-based index of the first occurrence of a specified value within an array. If the value isn’t found, the function returns -1. Use this function when you need to identify the position of a specific item within an array, such as finding the location of an error code in a sequence of logs or pinpointing a particular value within telemetry data 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_index_of(array, lookup_value, [start], [length], [occurrence])

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Parameters

NameTypeRequiredDescription
arrayarrayYesInput array to search.
lookup_valuescalarYesScalar value to search for in the array. Accepted data types: long, integer, double, datetime, timespan, or string.
start_indexnumberNoThe index where to start the search. A negative value offsets the starting search value from the end of the array by abs(start_index) steps.
lengthnumberNoNumber of values to examine. A value of -1 means unlimited length.
occurrencenumberNoThe number of the occurrence. By default 1.

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Returns

array_index_of returns the zero-based index of the first occurrence of the specified lookup_value in array. If lookup_value doesn’t exist in the array, it returns -1.

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Use case examples

You can use array_index_of to find the position of a specific HTTP status code within an array of codes in your log analysis.

Query

['sample-http-logs']
| take 50
| summarize status_array = make_list(status)
| extend index_500 = array_index_of(status_array, '500')

Run in Playground

Output

status_arrayindex_500
[“200”, “404”, “500”]2

This query creates an array of status codes and identifies the position of the first occurrence of the 500 status.

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