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Expression functions reference

An expression processor in Imply Lumi transforms string and numeric values as incoming events flow through a pipeline. Use this reference to find the functions you need to build your expressions.

CEIL​

CEIL(n)

For a numeric literal n, rounds up to the nearest integer.

Example

Rounds up the number of hours.

Expression
CEIL(hours)
Event input
{"hours": 5.8}
Expression output
hours: 6

COALESCE​

COALESCE(a, b, ...)

For two or more inputs, returns the first non-null, non-empty value.

Example

Determine when an order was last updated.

Expression
COALESCE(return_date, order_date, '1900-01-01')
Event input
{"order_date": "2026-01-28T06:19:54Z"}
Expression output
last_update: 2026-01-28T06:19:54Z

CONCAT​

CONCAT(a, b, ...)

For two or more inputs, joins into a single result.

Example

Combine first and last names.

Expression
CONCAT(firstName, '_', lastName)
Event input
{"firstName": "Wilma", "lastName": "Rudolph"}
Expression output
fullName: Wilma_Rudolph

FLOOR​

FLOOR(n)

For a numeric literal n, rounds down to the nearest integer.

Example

Rounds down a store's rating.

Expression
FLOOR(rating)
Event input
{"rating": 4.2}
Expression output
rating_bucket: 4

LENGTH​

LENGTH(s)

For string literal s, returns the number of characters.

Example

Get the length of a zip code.

Expression
LENGTH(zip)
Event input
{"zip": 92617}
Expression output
len_zip: 5

LOWER​

LOWER(s)

For string literal s, converts to lowercase.

Example

Normalize email address to lower case.

Expression
LOWER(email)
Event input
{"email": "User@Example.com"}
Expression output
email: user@example.com

LTRIM​

LTRIM(s)

For string literal s, removes leading whitespace.

Example

Strip leading spaces from fixed-width form field.

Expression
LTRIM(employee_id)
Event input
{"employee_id": " E4821"}
Expression output
employee_id: E4821

REPLACE​

REPLACE(s, pattern, replacement)

For string literal s, finds regex pattern and replaces it with replacement.

Example

Format a date from YYYY-MM-DD to MM/DD/YYYY.

Expression
REPLACE(raw_date, "(\d{4})-(\d{2})-(\d{2})", "$2/$3/$1")
Event input
{"raw_date": "2026-03-13"}
Expression output
formatted_date: 03/13/2026

ROUND​

ROUND(n, [precision])

For numeric literal n, rounds to the nearest integer or, if specified, to precision decimal places. Numbers halfway between two integers round up; for example, 4.5 rounds to 5.

Example

Rounds a price to two decimal places.

Expression
ROUND(price, 2)
Event input
{"price": 934.49032}
Expression output
price: 934.49

RTRIM​

RTRIM(s)

For string literal s, removes trailing whitespace.

Example

Strip trailing spaces from product code.

Expression
RTRIM(sku)
Event input
{"sku": "SKU001 "}
Expression output
sku: SKU001

SUBSTRING​

SUBSTRING(s, start, length)

For string literal s, extracts a substring starting at zero-based index start for length characters.

Example

Extract the date part of a filename.

Expression
SUBSTRING(filename, 4,6)
Event input
{"filename": "app_260313_error.log"}
Expression output
file_date: 260313

TRIM​

TRIM(s)

For string literal s, removes leading and trailing whitespace.

Example

Strip leading and trailing spaces from an extracted field.

Expression
TRIM(city)
Event input
{"city": " New Orleans "}
Expression output
city: New Orleans

UPPER​

UPPER(s)

For string literal s, converts to uppercase.

Example

Normalize state abbreviation to upper case.

Expression
UPPER(state)
Event input
{"state": "Ca"}
Expression output
state: CA

Learn more​

For more information, see the following topics:

Manage pipelines and processors for details on creating a pipeline. Processors reference for details on processors.