VARIF Function

Generates the variance of values by group in a column that meet a specific condition.

Nota

When added to a transform, 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. Transforms that change the number of rows in subsequent recipe steps do not affect the values computed for this step.

Terms...

Relevant terms:

Term

Description

Population

Population statistical functions are computed from all possible values. See https://en.wikipedia.org/wiki/Statistical_population.

Sample

Sample-based statistical functions are computed from a subset or sample of all values. See https://en.wikipedia.org/wiki/Sampling_(statistics).

These function names include SAMP in their name.

Nota

Statistical sampling has no relationship to the samples taken within the product. When statistical functions are computed during job execution, they are applied across the entire dataset. Sample method calculations are computed at that time.

• This function is calculated across the entire population.

• For more information on a sampled version of this function, see VARSAMPIF 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

varif(testScores, ((testScores &gt; 0) &amp;&amp; (testScores &lt; 90))

Output: Returns the variance of the testScores column when the testScores value is between 0 and 90.

Syntax and Arguments

varif(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 the group and limit parameters, 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

Suggerimento

Example - Conditional Calculation Functions

This example illustrates how to use the conditional calculation functions.

Functions:

Item

Description

AVERAGEIF Function

Generates the average value of rows in each group that meet a specific condition. Generated value is of Decimal type.

MINIF Function

Generates the minimum value of rows in each group that meet a specific condition. Inputs can be Integer, Decimal, or Datetime.

MAXIF Function

Generates the maximum value of rows in each group that meet a specific condition. Inputs can be Integer, Decimal, or Datetime.

VARIF Function

Generates the variance of values by group in a column that meet a specific condition.

STDEVIF Function

Generates the standard deviation of values by group in a column that meet a specific condition.

Source:

Here is some example weather data:

date

city

rain

temp

wind

1/23/17

Valleyville

0.00

12.8

6.7

1/23/17

Center Town

0.31

9.4

5.3

1/23/17

Magic Mountain

0.00

0.0

7.3

1/24/17

Valleyville

0.25

17.2

3.3

1/24/17

Center Town

0.54

1.1

7.6

1/24/17

Magic Mountain

0.32

5.0

8.8

1/25/17

Valleyville

0.02

3.3

6.8

1/25/17

Center Town

0.83

3.3

5.1

1/25/17

Magic Mountain

0.59

-1.7

6.4

1/26/17

Valleyville

1.08

15.0

4.2

1/26/17

Center Town

0.96

6.1

7.6

1/26/17

Magic Mountain

0.77

-3.9

3.0

1/27/17

Valleyville

1.00

7.2

2.8

1/27/17

Center Town

1.32

20.0

0.2

1/27/17

Magic Mountain

0.77

5.6

5.2

1/28/17

Valleyville

0.12

-6.1

5.1

1/28/17

Center Town

0.14

5.0

4.9

1/28/17

Magic Mountain

1.50

1.1

0.4

1/29/17

Valleyville

0.36

13.3

7.3

1/29/17

Center Town

0.75

6.1

9.0

1/29/17

Magic Mountain

0.60

3.3

6.0

Transformation:

The following computes average temperature for rainy days by city:

 Transformation Name New formula Single row formula AVERAGEIF(temp, rain > 0) city 'avgTempWRain'

The following computes maximum wind for sub-zero days by city:

 Transformation Name New formula Single row formula MAXIF(wind,temp < 0) city 'maxWindSubZero'

This step calculates the minimum temp when the wind is less than 5 mph by city:

 Transformation Name New formula Single row formula MINIF(temp,wind<5) city 'minTempWind5'

This step computes the variance in temperature for rainy days by city:

 Transformation Name New formula Single row formula VARIF(temp,rain >0) city 'varTempWRain'

The following computes the standard deviation in rainfall for Center Town:

 Transformation Name New formula Single row formula STDEVIF(rain,city=='Center Town') city 'stDevRainCT'

You can use the following transforms to format the generated output. Note the $col placeholder value for the multi-column transforms:  Transformation Name Edit column with formula stDevRainCenterTown,maxWindSubZero numformat($col,'##.##')

Since the following rely on data that has only one significant digit, you should format them differently:

 Transformation Name Edit column with formula varTempWRain,avgTempWRain,minTempWind5 numformat(\$col,'##.#')

Results:

date

city

rain

temp

wind

avgTempWRain

maxWindSubZero

minTempWind5

varTempWRain

stDevRainCT

1/23/17

Valleyville

0.00

12.8

6.7

8.3

5.1

7.2

63.8

0.37

1/23/17

Center Town

0.31

9.4

5.3

7.3

5

32.6

0.37

1/23/17

Magic Mountain

0.00

0.0

7.3

1.6

6.43

-3.9

12

0.37

1/24/17

Valleyville

0.25

17.2

3.3

8.3

5.1

7.2

63.8

0.37

1/24/17

Center Town

0.54

1.1

7.6

7.3

5

32.6

0.37

1/24/17

Magic Mountain

0.32

5.0

8.8

1.6

6.43

-3.9

12

0.37

1/25/17

Valleyville

0.02

3.3

6.8

8.3

5.1

7.2

63.8

0.37

1/25/17

Center Town

0.83

3.3

5.1

7.3

5

32.6

0.37

1/25/17

Magic Mountain

0.59

-1.7

6.4

1.6

6.43

-3.9

12

0.37

1/26/17

Valleyville

1.08

15.0

4.2

8.3

5.1

7.2

63.8

0.37

1/26/17

Center Town

0.96

6.1

7.6

7.3

5

32.6

0.37

1/26/17

Magic Mountain

0.77

-3.9

3.0

1.6

6.43

-3.9

12

0.37

1/27/17

Valleyville

1.00

7.2

2.8

8.3

5.1

7.2

63.8

0.37

1/27/17

Center Town

1.32

20.0

0.2

7.3

5

32.6

0.37

1/27/17

Magic Mountain

0.77

5.6

5.2

1.6

6.43

-3.9

12

0.37

1/28/17

Valleyville

0.12

-6.1

5.1

8.3

5.1

7.2

63.8

0.37

1/28/17

Center Town

0.14

5.0

4.9

7.3

5

32.6

0.37

1/28/17

Magic Mountain

1.50

1.1

0.4

1.6

6.43

-3.9

12

0.37

1/29/17

Valleyville

0.36

13.3

7.3

8.3

5.1

7.2

63.8

0.37

1/29/17

Center Town

0.75

6.1

9.0

7.3

5

32.6

0.37

1/29/17

Magic Mountain

0.60

3.3

6.0

1.6

6.43

-3.9

12

0.37