DOUBLEMETAPHONEEQUALS Function
Compares two input strings using the Double Metaphone algorithm. An optional threshold parameter can be modified to adjust the tolerance for matching.
The Double Metaphone algorithm processes an input string 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.
Sugerencia
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:
doublemetaphoneequals('My String', 'my string')
Output: Returns the value true
.
Column reference example:
doublemetaphoneequals(string1, string2, 'weak')
Output: Returns the comparison of string1
and string2
column values using the Double Metaphone algorithm. The 'weak'
parameter input means that only the secondary encodings for each input must match.
Syntax and Arguments
doublemetaphoneequals(string_ref1, string_ref2, match_threshold)
Argument | Required? | Data Type | Description |
---|---|---|---|
string_ref1 | Y | string | Name of first column or string literal to apply to the function |
string_ref2 | Y | string | Name of second column or string literal to apply to the function |
match_threshold | N | string | Optional string value for the matching threshold to use in the comparison. Default value is |
For more information on syntax standards, see Language Documentation Syntax Notes.
string_ref1, string_ref2
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 |
match_threshold
String literal identifying the threshold that determines a match according to the Double Metaphone encodings of the input strings. Accepted values:
Threshold Value | Description |
---|---|
'strong' | The primary encodings of the two input strings must match. |
'normal' | (Default) The primary encoding of one input string must match either of the encodings of the other input string. |
'weak' | Either primary or secondary encoding of one input string must match either encoding of the other input string. |
Usage Notes:
Required? | Data Type | Example Value |
---|---|---|
Yes | String literal | |
Examples
Sugerencia
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.
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 | |
---|---|
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 | |
---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | DOUBLEMETAPHONEEQUALS(string1, string2, 'normal') |
Parameter: New column name | 'compare' |
Results:
The following table contains some example strings to be compared.
string1 | dblmeta_s1 | string2 | compare | Notes |
---|---|---|---|---|
My String | ["MSTRNK","MSTRNK"] | my string | TRUE | comparison is case-insensitive |
judge | ["JJ","AJ"] | juge | TRUE | typo |
knock | ["NK","NK"] | nock | TRUE | silent letters |
white | ["AT","AT"] | wite | TRUE | missing letters |
record | ["RKRT","RKRT"] | record | TRUE | two different words in English but match the same |
pair | ["PR","PR"] | pear | TRUE | these match but are different words. |
bookkeeper | ["PKPR","PKPR"] | book keeper | FALSE | spaces cause failures in comparison |
test1 | ["TST","TST"] | test123 | TRUE | digits are not compared |
the end. | ["0NT","TNT"] | the end…. | TRUE | punctuation differences do not matter. |
a elephant | ["ALFNT","ALFNT"] | an elephant | FALSE | a and an are treated differently. |