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

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Computes an approximation for a specified percentile 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.
• 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.

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

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

approximatepercentile(myScores, 25)

Output: Computes the approximate value that is at the 25th percentile across all values in the myScores column.

## Syntax and Arguments

approximatepercentile(function_col_ref,num_percentile) [group:group_col_ref] [limit:limit_count]

ArgumentRequired?Data TypeDescription
function_col_refYstringName of column to which to apply the function
num_percentileYintegerInteger value between 1-100 of the percentile to compute
dec_error_boundNdecimalError factor for computing approximations. Decimal value represents error factor as a percentage (`0.4` is 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 percentile. 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_percentile

Integer literal value indicating the percentile that you wish to compute. Input value must be between `1` and `100`, inclusive.

• Column or function references are not supported.
• Multiple columns and wildcards are not supported.

Usage Notes:

Required?Data TypeExample Value
YesInteger`55`

### 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 TypeExample Value
NoDecimal (literal)```0.01 ```

## Examples

### 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` `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:

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

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