Excerpt 

Computes the rolling kth largest value forward or backward of the current row. 
KTHLARGEST
extracts the ranked value from the values in a column, where k=1
returns the maximum value. The value for k
must be between 1 and 1000, inclusive. For purposes of this calculation, two instances of the same value are treated as separate values. So, if your dataset contains three rows with column values 10
, 9
, and 9
, then KTHLARGEST
returns 9
for k=2
and k=3
.
ROLLINGKTHLARGEST
computes the KTHLARGEST
value across a defined window of values within a column.
 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 calculation 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.
 Inputs:
 Required column name
 Required kth value, which is a positive integer
 Two optional integer parameters that determine the window backward and forward of the current row. The default integer parameter values are
1
and 0
, which computes the rolling function from the current row back to the first row of the dataset.
 This function works with the following transforms:
For more information on a nonrolling version of this function, see KTHLARGEST Function.
Column example:
D code 

derive type:single value:ROLLINGKTHLARGEST(myCol, 2) 
Output: Generates a new column containing the rolling second largest of all values in the myCol
column from the first row of the dataset to the current one.
Rows before example:
D code 

window value:ROLLINGKTHLARGEST(myNumber, 2, 3) 
Output: Generates the new column, which contains the rolling second largest value of the current row and the two previous row values in the myNumber
column.
Rows before and after example:
D code 

window value:value:ROLLINGKTHLARGEST(myNumber, 4, 3, 2) 
Output: Generates the new column, which contains the rolling fourth largest value of the two previous row values, the current row value, and the two rows after the current one in the myNumber
column.
D code 

window value:value:ROLLINGKTHLARGEST(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 
k_integer  Y  integer (positive)  The ranking of the value to extract from the source column 
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.
col_ref
Name of the column whose values are used to compute the function.
 Multiple columns and wildcards are not supported.
Required?  Data Type  Example Value 

Yes  String (column reference to Integer or Decimal values)  myColumn 
k_integer
Integer representing the ranking of the unique value to extract from the source column. Duplicate values are treated as separate values for purposes of this function's calculation.
Info 

NOTE: The value for k must be an integer between 1 and 1,000 inclusive. 
k=1
represents the maximum value in the column.  If k is greater than or equal to the number of values in the column, the minimum value is returned.
 Missing and null values are not factored into the ranking of
k
.
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 four rows after it are used in the computation. Negative values for k
compute the rolling average from rows preceding the current one.
rowBefore=1
generates the current row value only.rowBefore=1
uses all rows preceding the current one. If
rowsAfter
is not specified, then the value 0
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.
Required?  Data Type  Example Value 

No  Integer  4 
Example  ROLLINGKTHLARGEST functions
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 EXAMPLE  ROLLINGKTHLARGEST Functions 

 EXAMPLE  ROLLINGKTHLARGEST Functions 

