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IFMISSING Function

The IFMISSING function writes out a specified value if the source value is a null or missing value. Otherwise, it writes the source value. Input can be a literal, a column reference, or a function.

  • The ISMISSING function simply tests if a value is missing. See ISMISSING Function.

  • Missing values are different from null values. To test for null values, see IFNULL Function.

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Since this function captures both missing and null values, you may first wish to address the rows with null values using the IFNULL or ISNULL functions. Any remaining rows that are matched based on this function are exclusively missing values.

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

ifmissing(my_score,'0')

Output: Generates a new column called, final_score, which contains the value 0 if the value in my_score is a null or missing value.

Syntax and Arguments

ifmissing(column_string, computed_value)

Argument

Required?

Data Type

Description

source_value

Y

string

Name of column, string literal or function to be tested

output_value

y

string

String literal value to write

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

source_value

Name of the column, string literal, or function to be tested for missing values.

  • Missing literals or column values generate missing string results.

  • Multiple columns and wildcards are not supported.

Usage Notes:

Required?

Data Type

Example Value

Yes

String literal, column reference, or function

myColumn

output_value

The output value to write if the tested value returns a null or missing value.

Usage Notes:

Required?

Data Type

Example Value

Yes

String or numeric literal

'Missing input'

Examples

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For additional examples, see Common Tasks.

Example - IF* functions for data type validation

This example illustrates how to use the IF* functions for data type validation.

Functions:

Item

Description

IFNULL Function

The IFNULL function writes out a specified value if the source value is a null. Otherwise, it writes the source value. Input can be a literal, a column reference, or a function.

IFMISSING Function

The IFMISSING function writes out a specified value if the source value is a null or missing value. Otherwise, it writes the source value. Input can be a literal, a column reference, or a function.

IFMISMATCHED Function

The IFMISMATCHED function writes out a specified value if the input expression does not match the specified data type or typing array. Otherwise, it writes the source value. Input can be a literal, a column reference, or a function.

IFVALID Function

The IFVALID function writes out a specified value if the input expression matches the specified data type. Otherwise, it writes the source value. Input can be a literal, a column reference, or a function.

MERGE Function

Merges two or more columns of String type to generate output of String type. Optionally, you can insert a delimiter between the merged values.

Source:

The following simple table lists zip codes by customer identifier:

custId

custZip

C001

98123

C002

94105

C003

12415

C004

12451-2234

C005

12441-298

C006

C007

C008

1242

C009

1104

Transformation:

When the above is imported into the Transformer page, you notice the following:

  • The custZip column is typed as Integer.

  • There are two missing and two mismatched values in the custZip column.

First, you test for valid values in the custZip column. Using the IFVALID function, you can validate against any data type:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

IFVALID(custZip, 'Zipcode', 'ok')

Parameter: New column name

'status'

Fix four-digit zips: In the status column are instances of ok for the top four rows. You notice that the bottom two rows contain four-digit codes.

Since the custZip values were originally imported as Integer, any leading 0 values are deleted. In this case, you can add back the leading zero. Before the previous step, change the data type of zip to String and insert the following:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

IF(LEN(custZip)==4,'0','')

Parameter: New column name

'FourDigitZip'

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

MERGE([FourDigitZip,custZip])

Parameter: New column name

'custZip2'

Transformation Name

Edit column with formula

Parameter: Columns

zip

Parameter: Formula

custZip2

Transformation Name

Delete columns

Parameter: Columns

FourDigitZip,custZip2

Parameter: Action

Delete selected columns

Now, when you click the last recipe step, you should see that two more rows in status are listed as Ok.

For the zip code with the three-digit extension, you can simply remove that extension to make it valid. Click the step above the last one. In the data grid, highlight the value. Click the Replace suggestion card. Select the option that uses the following for the matching pattern:

'-{digit}{3}{end}'

The above means that all three-digit extensions are deleted from the zip. You can do the same for any two- and one-digit extensions, although there are none in this sample.

Missing and null values: Now, you need to address how to handle missing and null values. The IFMISSING tests for both missing and null values, while the IFNULL tests just for null values. In this example, you want to delete null values, which could mean that the data for that row is malformed and to write a status of missing for missing values.

Click above the last line in the recipe to insert the following:

Transformation Name

Edit column with formula

Parameter: Columns

custZip

Parameter: Formula

IFNULL(custZip, 'xxxxx')

Transformation Name

Edit column with formula

Parameter: Columns

custZip

Parameter: Formula

IFMISSING(custZip, '00000')

Now, when you click the last line of the recipe, only the null value is listed as having a status other than ok. You can use the following to remove this row and all like it:

Transformation Name

Filter rows

Parameter: Condition

Custom formula

Parameter: Type of formula

Custom single

Parameter: Condition

(status == 'xxxxx')

Parameter: Action

Delete matching rows

Results:

custId

custZip

status

C001

98123

ok

C002

94105

ok

C003

12415

ok

C004

12451-2234

ok

C005

12441-298

ok

C006

00000

ok

C008

1242

ok

C009

1104

ok

As an exercise, you might repeat the above steps starting with the IFMISMATCHED function determining the value in the status column:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

IFMISMATCHED(custZip, 'Zipcode', 'mismatched')

Parameter: New column name

'status'