ROLLINGMODE Function
Computes the rolling mode (most common value) forward or backward of the current row within the specified column. Input values can be Integer, Decimal, or Datetime data type.
If an input value is missing or null, it is not factored in the computation. For example, for the first row in the dataset, the rolling mode of previous values is undefined.
The row from which to extract a value is determined by the order in which the rows are organized based on the
orderparameter.If you are working on a randomly generated sample of your dataset, the values that you see for this function might not correspond to the values that are generated on the full dataset during job execution.
The function takes a column name and two optional integer parameters that determine the window backward and forward of the current row.
The default integer parameter values are
-1and0, which computes the rolling function from the current row back to the first row of the dataset.
This function works with the Window transform. See Window Transform.
For more information on a non-rolling version of this function, see MODE 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
Column example:
rollingmode(myCol)
Output: Returns the rolling mode of all values in the myCol column.
Rows before example:
rollingmode(myNumber, 3)
Output: Returns the rolling mode of the current row and the three previous row values in the myNumber column.
Rows before and after example:
rollingmode(myNumber, 3, 2)
Output: Returns the rolling mode of the three previous row values, the current row value, and the two rows after the current one in the myNumber column.
Syntax and Arguments
rollingmode(col_ref, rowsBefore_integer, rowsAfter_integer) order: order_col [group: group_col]
Argument | Required? | Data Type | Description |
|---|---|---|---|
col_ref | Y | string | Name of column whose values are applied to the function |
rowsBefore_integer | N | integer | Number of rows before the current one to include in the computation |
rowsAfter_integer | N | integer | Number of rows after the current one to include in the computation |
For more information on the order and group parameters, see Window Transform.
For more information on syntax standards, see Language Documentation Syntax Notes.
col_ref
Name of the column whose values are used to compute the function.
注記
If the input is in Datetime type, the output is in unixtime format. You can wrap these outputs in the DATEFORMAT function to generate the results in the appropriate Datetime format. See DATEFORMAT Function.
Multiple columns and wildcards are not supported.
Usage Notes:
Required? | Data Type | Example Value |
|---|---|---|
Yes | String (column reference to Integer or Decimal values) | myColumn |
rowsBefore_integer, rowsAfter_integer
Integers representing the number of rows before or after the current one from which to compute the rolling function, including the current row. For example, if the first value is 5, the current row and the five rows before it are used in the computation. Negative values for rowsAfter_integer compute the rolling function from rows preceding the current one.
rowBefore=0generates the current row value only.rowBefore=-1uses all rows preceding the current one.If
rowsAfteris not specified, then the value0is applied.If a
groupparameter is applied, then these parameter values should be no more than the maximum number of rows in the groups.
Usage Notes:
Required? | Data Type | Example Value |
|---|---|---|
No | Integer | 4 |
Examples
ヒント
For additional examples, see Common Tasks.
Example - Counting most common coin flips
In the following table, 20 coin flips are tabulated. You want to capture a rolling evaluation of the most common value.
Source:
Turn | Result |
|---|---|
1 | heads |
2 | heads |
3 | tails |
4 | heads |
5 | heads |
6 | tails |
7 | tails |
8 | heads |
9 | tails |
10 | heads |
11 | tails |
12 | heads |
13 | tails |
14 | heads |
15 | heads |
16 | tails |
17 | tails |
18 | tails |
19 | heads |
20 | heads |
Transformation:
To use the ROLLINGMODE function, the results need to be converted to numeric values:
Transformation Name | |
|---|---|
Parameter: Columns | Result |
Parameter: Formula | if(Result == 'heads', 0, 1) |
Now calculate the ROLLINGMODE for the preceding five values for each row:
Transformation Name | |
|---|---|
Parameter: Formula type | Multiple row formula |
Parameter: Formula | rollingmode(Result, 4, 0) |
Parameter: Sort rows by | Turn |
Parameter: New column name | 'mostCommonLast5' |
You can now convert the binary values back to text information:
Transformation Name | |
|---|---|
Parameter: Columns | mostCommonLast5 |
Parameter: Formula | if(mostCommonLast5 == 0, 'heads-last5', 'tails-last5') |
Results:
Turn | Result | mostCommonLast5 |
|---|---|---|
1 | heads | heads-last5 |
2 | heads | heads-last5 |
3 | tails | heads-last5 |
4 | heads | heads-last5 |
5 | heads | heads-last5 |
6 | tails | heads-last5 |
7 | tails | tails-last5 |
8 | heads | heads-last5 |
9 | tails | tails-last5 |
10 | heads | tails-last5 |
11 | tails | tails-last5 |
12 | heads | heads-last5 |
13 | tails | tails-last5 |
14 | heads | heads-last5 |
15 | heads | heads-last5 |
16 | tails | heads-last5 |
17 | tails | tails-last5 |
18 | tails | tails-last5 |
19 | heads | tails-last5 |
20 | heads | tails-last5 |