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.
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
pivottransform, 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.
For an exact calculation of this function, see PERCENTILE 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
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]
Argument | Required? | Data Type | Description |
|---|---|---|---|
function_col_ref | Y | string | Name of column to which to apply the function |
num_percentile | Y | integer | Integer value between 1-100 of the percentile to compute |
dec_error_bound | N | decimal | Error factor for computing approximations. Decimal value represents error factor as a percentage ( |
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 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 Type | Example Value |
|---|---|---|
Yes | String (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 Type | Example Value |
|---|---|---|
Yes | Integer | 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 Type | Example Value |
|---|---|---|
No | Decimal (literal) | 0.01 |
Examples
Astuce
For additional examples, see Common Tasks.
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 | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | median(heightIn) |
Parameter: New column name | 'medianIn' |
Transformation Name | |
|---|---|
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 | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | percentile(heightIn, 68, linear) |
Parameter: New column name | 'percentile68In' |
Transformation Name | |
|---|---|
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 | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | quartile(heightIn, 1, linear) |
Parameter: New column name | 'percentile25In' |
Transformation Name | |
|---|---|
Parameter: Formula type | Single row formula |
Parameter: Formula | approximatequartile(heightIn, 1, 0.4) |
Parameter: New column name | '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 |