I'm trying to split a data set into two random fragments, and my code isn't working

Question

I'm trying to do this simple task, all the variables are initialized properly, but for some reason this isn't working. What am I doing wrong?

for(i in 1:117) 
  {x = runif(1,0,1)
   if(x<0.5) 
     testframe = rbind(utilities[i,]) 
   else 
     trainframe = rbind(utilities[i,])}

Answer 1

In your loop, you overwrite both testframe and trainframe in each run of the loop. You could use testframe <- rbind(testframe, utilities[i, ]), but this would be quite inefficient.

Here's another approach without loops:

x <- sample(c(TRUE, FALSE), 117, replace = TRUE)

testframe <- utilities[x, ]
trainframe <- utilities[!x, ]

You can also create a list including the two subsets (based on vector x):

split(utilities, x)

Answer 2

If you insist to use a for loop, you can always save your outcome as an empty list and add items to that list:

Here's an untested example (as I do not have the "utilities" data):

testframe <- list()
trainframe <- list()

for(i in 1:117) 
  {x = runif(1,0,1)
   if(x<0.5) 
     testframe[i] <- utilities[i,] ##whatever you want to save here
   else 
     trainframe = utilities[i,]
}

Hope this helps