[R] Sampling with Constraints for testing and training data

[Eliano]

Hi People, 

Does anyone have a good solution for this problem: 

a database called DB. 


index <- sample(1:nrow(DB), size=0.2*nrow(BD)) 
test <- DB[index,] 
train <- DB[-index,] 

One of the variables in this database contais a target variable with two
values 0 and 1. 

Imagine now that i want to constraint the test data frame so the 20% of the
size of "test" has 50% of DB$target. 

Imagine: n=100 
DB$target = { 0=80 
                           1=20} 

test=20 and contain 10 random values of DB$target=1 and 10 random values of
DB$target=0. 



Many Thanks, 
Eliano 



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