# APPROXIMATEQUARTILE Function

Computes an approximation for a specified quartile across all row values in a column or group. Input column can be of Integer or Decimal.

• If a row contains a missing or null value, it is not factored into the calculation. If the entire column contains no values, the function returns a null value.

• When used in apivottransform, the function is computed for each instance of the value specified in thegroupparameter. See Pivot Transform.

• The approximate percentile functions utilize a different algorithm for efficiently estimating quantiles for streaming and distributed processing, depending on the running environment where the function is computed.

Astuce

Approximation functions are suitable for larger datasets. As the number of rows increases, accuracy and calculation performance improves for these functions.

Quartiles are computed as follows:

Quartile

Description

0

Minimum value

1

25th percentile

2

Median value

3

75th percentile and higher

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

<span>approximatequartile</span>(myScores, 3)

Output: Computes the approximate value that is at the 3rd quartile across all values in the myScores column.

## Syntax and Arguments

approximatequartile(function_col_ref,num_quartile) [group:group_col_ref] [limit:limit_count]

Argument

Required?

Data Type

Description

function_col_ref

Y

string

Name of column to which to apply the function

num_quartile

Y

integer

Integer value (0-3) of the quartile to compute

dec_error_bound

N

decimal

Error factor for computing approximations. Decimal value represents error factor as a percentage (0.4is 0.4%).

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

### function_col_ref

Name of the column the values of which you want to calculate the quartile. Column must contain Integer or Decimal values.

• Literal values are not supported as inputs.

• Multiple columns and wildcards are not supported.

Usage Notes:

Required?

Data Type

Example Value

Yes

String (column reference)

precipitationIn

### num_quartile

Integer literal value indicating the quartile that you wish to compute. Input value must be between 0 and 3, inclusive.

• Column or function references are not supported.

• Multiple columns and wildcards are not supported.

Usage Notes:

Required?

Data Type

Example Value

Yes

Integer

3

### dec_error_bound

As needed, you can insert an error boundary factor as a parameter into the computation of this approximate value.

• This value must be a Decimal literal value.

• This decimal value represents the percentage error factor. By default, this value is 0.5 (0.5%).

Usage Notes:

Required?

Data Type

Example Value

No

Decimal (literal)

0.01

## Examples

Astuce

### Example - Percentile functions

This example illustrates you to apply percentile functions.

Functions:

Item

Description

MEDIAN Function

Computes the median from all row values in a column or group. Input column can be of Integer or Decimal.

PERCENTILE Function

Computes a specified percentile across all row values in a column or group. Input column can be of Integer or Decimal.

QUARTILE Function

Computes a specified quartile across all row values in a column or group. Input column can be of Integer or Decimal.

APPROXIMATEMEDIAN Function

Computes the approximate median from all row values in a column or group. Input column can be of Integer or Decimal.

APPROXIMATEPERCENTILE Function

Computes an approximation for a specified percentile across all row values in a column or group. Input column can be of Integer or Decimal.

APPROXIMATEQUARTILE Function

Computes an approximation for a specified quartile across all row values in a column or group. Input column can be of Integer or Decimal.

Source:

The following table lists each student's height in inches:

Student

Height

1

64

2

65

3

63

4

64

5

62

6

66

7

66

8

65

9

69

10

66

11

73

12

69

13

69

14

61

15

64

16

61

17

71

18

67

19

73

20

66

Transformation:

Use the following transformations to calculate the median height in inches, a specified percentile and the first quartile.

• The first function uses a precise algorithm which can be slow to execute across large datasets.

• The second function uses an appropriate approximation algorithm, which is much faster to execute across large datasets.

• These approximate functions can use an error boundary parameter, which is set to 0.4 (0.4%) across all functions.

Median: This transformation calculates the median value, which corresponds to the 50th percentile.

 Transformation Name New formula Single row formula median(heightIn) 'medianIn'
 Transformation Name New formula Single row formula approximatemedian(heightIn, 0.4) 'approxMedianIn'

Percentile: This transformation calculates the 68th percentile.

 Transformation Name New formula Single row formula percentile(heightIn, 68, linear) 'percentile68In'
 Transformation Name New formula Single row formula approximatepercentile(heightIn, 68, 0.4) 'approxPercentile68In'

Quartile: This transformation calculates the first quartile, which corresponds to the 25th percentile.

 Transformation Name New formula Single row formula quartile(heightIn, 1, linear) 'percentile25In'
 Transformation Name New formula Single row formula approximatequartile(heightIn, 1, 0.4) 'approxPercentile25In'

Results:

studentId

heightIn

approxPercentile25In

percentile25In

approxPercentile68In

percentile68In

approxMedianIn

medianIn

1

64

64

64

67.1

66.92

66

66

2

65

64

64

67.1

66.92

66

66

3

63

64

64

67.1

66.92

66

66

4

64

64

64

67.1

66.92

66

66

5

62

64

64

67.1

66.92

66

66

6

66

64

64

67.1

66.92

66

66

7

66

64

64

67.1

66.92

66

66

8

65

64

64

67.1

66.92

66

66

9

69

64

64

67.1

66.92

66

66

10

66

64

64

67.1

66.92

66

66

11

73

64

64

67.1

66.92

66

66

12

69

64

64

67.1

66.92

66

66

13

69

64

64

67.1

66.92

66

66

14

61

64

64

67.1

66.92

66

66

15

64

64

64

67.1

66.92

66

66

16

61

64

64

67.1

66.92

66

66

17

71

64

64

67.1

66.92

66

66

18

67

64

64

67.1

66.92

66

66

19

73

64

64

67.1

66.92

66

66

20

66

64

64

67.1

66.92

66

66