DOUBLEMETAPHONE Function

Returns a two-element array of primary and secondary phonetic encodings for an input string, based on the Double Metaphone algorithm.

The Double Metaphone algorithm processes an input string to render a primary and secondary spelling for it. For English language words, the algorithm removes silent letters, normalizes combinations of characters to a single definition, and removes vowels, except from the beginnings of words. In this manner, the algorithm can normalize inconsistencies between spellings for better matching. For more information, see https://en.wikipedia.org/wiki/Metaphone.

Tip

This function is useful for performing fuzzy matching between string values, such as between potential join key values.

Source values can be string literals, column references, or expressions that evaluate to strings.

Wrangle vs. SQL: This function is part of Wrangle, a proprietary data transformation language. Wrangle is not SQL. For more information, see Wrangle Language.

Basic Usage

String literal reference example:

doublemetaphone('My String')

Output: See below.

["MSTRNK","MSTRNK"]

Column reference example:

doublemetaphone(string1)

Output: Generates a new double_metaphone column containing the evaluation of string1 column values through the Double Metaphone algorithm.

Syntax and Arguments

doublemetaphone(string_ref)

Argument	Required?	Data Type	Description
string_ref	Y	string	Name of column or string literal to apply to the function

For more information on syntax standards, see Language Documentation Syntax Notes.

string_ref1

String literal, column reference, or expression whose elements you want to filter through the Double Metaphone algorithm.

Usage Notes:

Required?	Data Type	Example Value
Yes	String literal, column reference, or expression evaluating to a string	myString1

Examples

Tip

For additional examples, see Common Tasks.

Example - Phonetic string comparisons

This example illustrates how to use double metaphone functions to generate phonetic spellings in Designer Cloud Powered by Trifacta Enterprise Edition.

Functions:

Item	Description
DOUBLEMETAPHONE Function	Returns a two-element array of primary and secondary phonetic encodings for an input string, based on the Double Metaphone algorithm.
DOUBLEMETAPHONEEQUALS Function	Compares two input strings using the Double Metaphone algorithm. An optional threshold parameter can be modified to adjust the tolerance for matching.

Source:

The following table contains some example strings to be compared.

string1	string2	notes
My String	my string	comparison is case-insensitive
judge	juge	typo
knock	nock	silent letters
white	wite	missing letters
record	record	two different words in English but match the same
pair	pear	these match but are different words.
bookkeeper	book keeper	spaces cause failures in comparison
test1	test123	digits are not compared
the end.	the end….	punctuation differences do not matter.
a elephant	an elephant	a and an are treated differently.

Transformation:

You can use the DOUBLEMETAPHONE function to generate phonetic spellings, as in the following:

Transformation Name	`New formula`
Parameter: Formula type	Single row formula
Parameter: Formula	DOUBLEMETAPHONE(string1)
Parameter: New column name	'dblmeta_s1'

You can compare string1 and string2 using the DOUBLEMETAPHONEEQUALS function:

Transformation Name	`New formula`
Parameter: Formula type	Single row formula
Parameter: Formula	DOUBLEMETAPHONEEQUALS(string1, string2, 'normal')
Parameter: New column name	'compare'

Results: