Page tree

NOTE:  Trifacta Wrangler is a free product with limitations on its features. Some features in the documentation do not apply to this product edition. See Product Limitations.

   

Contents:


Computes 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 a pivot transform, the function is computed for each instance of the value specified in the group parameter. See Pivot Transform.

Quartiles are computed as follows:

QuartileDescription
0Minimum value
125th percentile
2Median value
375th 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>quartile</span>(myScores, 3, linear)

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

Syntax and Arguments

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


ArgumentRequired?Data TypeDescription
function_col_refYstringName of column to which to apply the function
num_quartileYintegerInteger value (0-3) of the quartile to compute
interpolation_methodYenumMethod by which to interpolate values between two row values. See below.

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

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

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 TypeExample Value
YesString (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 TypeExample Value
YesInteger3

interpolation_method

Method of interpolation between each discrete value. The list of support methods is the following:

Interpolation methodDescription
linearQuartiles are calculated between two discrete values in a linear fashion.
exclusiveExcludes 0 (0th percentile) and 1 (100th percentile) from calculation of quartiles.
inclusiveIncludes 0 (0th percentile) and 1 (100th percentile) from calculation of quartiles.
lowerUse the lower value when the computed value falls between two discrete values.
upperUse the upper value when the computed value falls between two discrete values.
midpointUse the midpoint value when the computed value falls between two discrete values.


Usage Notes:

Required?Data TypeExample Value
YesEnumlinear

Examples


Tip: For additional examples, see Common Tasks.

Example - Percentile functions

This example illustrates you to apply percentile functions.

Functions:

ItemDescription
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:

StudentHeight
164
265
363
464
562
666
766
865
969
1066
1173
1269
1369
1461
1564
1661
1771
1867
1973
2066

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
Parameter: Formula type Single row formula
Parameter: Formula median(heightIn)
Parameter: New column name 'medianIn'

Transformation Name New formula
Parameter: Formula type Single row formula
Parameter: Formula approximatemedian(heightIn, 0.4)
Parameter: New column name 'approxMedianIn'

Percentile: This transformation calculates the 68th percentile.

Transformation Name New formula
Parameter: Formula type Single row formula
Parameter: Formula percentile(heightIn, 68, linear)
Parameter: New column name 'percentile68In'

Transformation Name New formula
Parameter: Formula type Single row formula
Parameter: Formula approximatepercentile(heightIn, 68, 0.4)
Parameter: New column name 'approxPercentile68In'

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

Transformation Name New formula
Parameter: Formula type Single row formula
Parameter: Formula quartile(heightIn, 1, linear)
Parameter: New column name 'percentile25In'

Transformation Name New formula
Parameter: Formula type Single row formula
Parameter: Formula approximatequartile(heightIn, 1, 0.4)
Parameter: New column name 'approxPercentile25In'

Results:

studentIdheightInapproxPercentile25Inpercentile25InapproxPercentile68Inpercentile68InapproxMedianInmedianIn
164646467.166.926666
265646467.166.926666
363646467.166.926666
464646467.166.926666
562646467.166.926666
666646467.166.926666
766646467.166.926666
865646467.166.926666
969646467.166.926666
1066646467.166.926666
1173646467.166.926666
1269646467.166.926666
1369646467.166.926666
1461646467.166.926666
1564646467.166.926666
1661646467.166.926666
1771646467.166.926666
1867646467.166.926666
1973646467.166.926666
2066646467.166.926666

This page has no comments.