Excerpt 

The RAND function generates a random real number between 0 and 1. The function accepts an optional integer parameter, which causes the same set of random numbers to be generated with each job execution. 
 This function generates values of Decimal type with fifteen digits of precision after the decimal point. If you want to see all digits in the generated value, you might need to apply a different number format. See NUMFORMAT Function.
 New random numbers are generated within the browser, after each browser refresh, and between subsequent job executions.
Optionally, you can insert an integer as a parameter.
 When this value is present, this seed value is used as part of the random number generator such that its output is a set of pseudorandom values, which are consistent between job executions.
 When the browser is refreshed, the random numbers remain consistent when the seed value is present.
 This value must be a valid literal Integer value. For more information on valid values, see Integer Data Type.
 If none is provided, a seed is generated based on the system timestamp.
Column references or functions returning Integer values are not supported.
Example:
D lang syntax 

RawWrangle  true 

Type  ref 

showNote  true 

WrangleText  derive type:single value: rand() as:'random' 


rand() 
Output: For each row, generate a random number between 0 and 1 in the new random
function.
Example with seed value:
D lang syntax 

RawWrangle  true 

Type  ref 

showNote  true 

WrangleText  derive type:single value: rand(2) as:'random' 


rand(2) 
Output: For each row, generate a random number between 0 and 1 in the new random
function. The generated random set of random values are consistent between job executions and are, in part, governed by the seed value 2
.
There are no arguments for this function.
D lang syntax 

RawWrangle  true 

Type  syntax 

showNote  true 

WrangleText  derive type:single value: rand([int_value]) 


rand([int_value]) 
Argument  Required?  Data Type  Description 

int_value  N  integer  Integer literal 
int_value
Optional Integer literal that is used to generate random numbers. Use of a seed value ensures consistency of output between job executions.
 This value must be a valid literal Integer value. For more information on valid values, see Integer Data Type.
 Literal numeric values should not be quoted. Quoted values are treated as strings.
 Multiple columns and wildcards are not supported.
Required?  Data Type  Example Value 

No  Integer literal  14 
Example  Random values
In the following example, the random
column is generated by the RAND
function:
D trans 

RawWrangle  true 

p03Value  'random' 

Type  step 

WrangleText  derive type:single value:rand() as:'random' 

p01Name  Formula type 

p01Value  Single row formula 

p02Name  Formula 

p02Value  rand() 

p03Name  New column name 

SearchTerm  New formula 


source  random 

A  0.516845703365675

B  0.71118736300207

C  0.758686066027118

D  0.640146255791255

Example  Type check functions
The RAND
function is typically used to introduce randomness of some kind in your data. In the following example, it is used to perform sampling within your wider dataset.
Source:
You want to extract a random sample of 20% of your set of orders for further study:
OrderId  Qty  ProdId 

1001  30  Widgets 
1002  10  Big Widgets 
1003  5  Big Widgets 
1004  40  Widgets 
1005  80  Tiny Widgets 
1006  20  Widgets 
1007  100  Tiny Widgets 
Transformation:
You can use the following transform to generate a random integer from one to 10:
D trans 

RawWrangle  true 

p03Value  'random' 

Type  step 

WrangleText  derive type:single value:round(rand() * 10) as:'random' 

p01Name  Formula type 

p01Value  Single row formula 

p02Name  Formula 

p02Value  round(rand() * 10) 

p03Name  New column name 

SearchTerm  New formula 


You can now use the following transform to keep only the rows that contain random values that are in the top 20%, where the value is 9
or 10
:
D trans 

RawWrangle  true 

p03Value  (random > 8) 

Type  step 

WrangleText  keep row:(random > 8) 

p01Name  Condition 

p01Value  Custom formula 

p02Name  Type of formula 

p02Value  Custom single 

p03Name  Condition 

p04Value  Keep matching rows 

p04Name  Action 

SearchTerm  Filter rows 


Results:
Info 

NOTE: Since the results are randomized, your results might vary. 
OrderId  Qty  ProdId  random 

1005  80  Tiny Widgets  9 
1007  100  Tiny Widgets  10 