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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
order
parameter.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
-1
and0
, which computes the rolling function from the current row back to the first row of the dataset.
- The default integer parameter values are
- This function works with the Window transform. See Window Transform.
For more information on a non-rolling version of this function, see MODE Function.
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Column example:
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rollingmode(myCol) |
Output: Returns the rolling mode of all values in the myCol
column.
Rows before example:
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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:
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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.
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rollingmode(col_ref, rowsBefore_integer, rowsAfter_integer) order: order_col [group: group_col] |
Argument | Required? | Data Type | Description |
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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.
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col_ref
Name of the column whose values are used to compute the function.
Info |
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NOTE: 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.
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Required? | Data Type | Example Value |
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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=0
generates the current row value only.rowBefore=-1
uses all rows preceding the current one.- If
rowsAfter
is not specified, then the value0
is applied. - If a
group
parameter is applied, then these parameter values should be no more than the maximum number of rows in the groups.
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Required? | Data Type | Example Value |
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No | Integer | 4 |
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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 |
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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:
D trans RawWrangle true Type step WrangleText set col: Result value: if(Result == 'heads', 0, 1) p01Name Columns p01Value Result p02Name Formula p02Value if(Result == 'heads', 0, 1) SearchTerm Edit column with formula
Now calculate the ROLLINGMODE
for the preceding five values for each row:
D trans RawWrangle true p03Value Turn Type step WrangleText derive type: multiple value: rollingmode(Result, 4, 0) order: Turn as: 'mostCommonLast5' p01Name Formula type p01Value Multiple row formula p02Name Formula p02Value rollingmode(Result, 4, 0) p03Name Sort rows by p04Value 'mostCommonLast5' p04Name New column name SearchTerm New formula
You can now convert the binary values back to text information:
D trans RawWrangle true Type step WrangleText set col: mostCommonLast5 value: if(mostCommonLast5 == 0, 'heads-last5', 'tails-last5') p01Name Columns p01Value mostCommonLast5 p02Name Formula p02Value if(mostCommonLast5 == 0, 'heads-last5', 'tails-last5') SearchTerm Edit column with formula
Results:
Turn | Result | mostCommonLast5 |
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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 |
D s also label window