Page tree

Trifacta SaaS


Contents:

 

Computes the median from 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.

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

median(myRating)

Output: Returns the median of the values in the myRating column.

Syntax and Arguments

median(function_col_ref) [group:group_col_ref] [limit:limit_count]


ArgumentRequired?Data TypeDescription
function_col_refYstringName of column to which to apply the function

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 median. 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)myValues

Examples

Tip: For additional examples, see Common Tasks.

Example - Percentile functions

This example illustrates how you can apply the following percentile-related functions to your transformations:
  • MEDIAN - Calculate the median value from a column of values. See MEDIAN Function.
  • PERCENTILE - Calculate a specified percentile for a column of values. See PERCENTILE Function.
  • QUARTILE - Calculate a specified quartile for a column of values. See QUARTILE Function.

The following functions use an approximation technique for calculating median, percentile, and quartiles. In some cases, these calculations can be computed faster across large datasets.

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.