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COUNTDISTINCTIF Function

Generates the count of distinct non-null values for rows in each group that meet a specific condition.

Note

When added to a transformation, this function is applied to the current sample. If you change your sample or run the job, the computed values for this function are updated. Transformations that change the number of rows in subsequent recipe steps do not affect the values computed for this step.

To perform a simple counting of distinct non-nulls without conditionals, use the COUNTDISTINCT function. See COUNTDISTINCT Function.

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

countdistinctif(entries, entryValidation == 'Ok')

Output: Generates a two-column table containing the unique values for City and the count of distinct non-null values in the entries column for that City value when the entryValidation value is 'Ok'. The limit parameter defines the maximum number of output columns.

Syntax and Arguments

countdistinctif(col_ref, test_expression) [group:group_col_ref] [limit:limit_count]

Argument

Required?

Data Type

Description

col_ref

Y

string

Reference to the column you wish to evaluate.

test_expression

Y

string

Expression that is evaluated. Must resolve to true or false

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

For more information on the group and limit parameter, see Pivot Transform.

col_ref

Name of the column whose values you wish to use in the calculation. Column must be a numeric (Integer or Decimal) type.

Usage Notes:

Required?

Data Type

Example Value

Yes

String that corresponds to the name of the column

myValues

test_expression

This parameter contains the expression to evaluate. This expression must resolve to a Boolean (true or false) value.

Usage Notes:

Required?

Data Type

Example Value

Yes

String expression that evaluates to true or false

(LastName == 'Mouse' && FirstName == 'Mickey')

Examples

Tip

For additional examples, see Common Tasks.

Example - Summarize Voter Registrations

This example illustrates how you can use conditional calculation functions.

Functions:

Item

Description

SUMIF Function

Generates the sum of rows in each group that meet a specific condition.

COUNTDISTINCTIF Function

Generates the count of distinct non-null values for rows in each group that meet a specific condition.

Source:

Here is some example polling data across 16 precincts in 8 cities across 4 counties, where registrations have been invalidated at the polling station, preventing voters from voting. Precincts where this issue has occurred previously have been added to a watch list (precinctWatchList).

totalReg

invalidReg

precinctWatchList

precinctId

cityId

countyId

731

24

y

1

1

1

743

29

y

2

1

1

874

0

3

2

1

983

0

4

2

1

622

29

5

3

2

693

0

6

3

2

775

37

y

7

4

2

1025

49

y

8

4

2

787

13

9

5

3

342

0

10

5

3

342

39

y

11

6

3

387

28

y

12

6

3

582

59

13

7

4

244

0

14

7

4

940

6

y

15

8

4

901

4

y

16

8

4

Transformation:

First, you want to sum up the invalid registrations (invalidReg) for precincts that are already on the watchlist (precinctWatchList = y). These sums are grouped by city, which can span multiple precincts:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

SUMIF(invalidReg, precinctWatchList == "y")

Parameter: Group rows by

cityId

Parameter: New column name

'invalidRegbyCityId'

The invalidRegbyCityId column contains invalid registrations across the entire city.

Now, at the county level, you want to identify the number of precincts that were on the watch list and were part of a city-wide registration problem.

In the following step, the number of cities in each count are counted where invalid registrations within a city is greater than 60.

  • This step creates a pivot aggregation.

Transformation Name

Pivot columns

Parameter: Row labels

countyId

Parameter: Values

COUNTDISTINCTIF(precinctId, invalidRegbyCityId > 60)

Parameter: Max number of columns to create

1

Results:

countyId

countdistinctif_precinctId

1

0

2

2

3

2

4

0

The voting officials in counties 2 and 3 should investigate their precinct registration issues.

In this section: