How to create a binary variable from a loop and an if statement
for-loop, if-statement, r
Solution
This can be done using vectorized operations instead of a loop:
> x <- runif(20, 0, 2)
> y <- as.integer(x > 1)
> x
[1] 0.06553935 1.23221386 0.39982502 0.27821193 1.15281280 0.14248373 0.09206153 1.63555223 0.44962775 0.70711450
[11] 0.93994130 1.41955732 1.95790383 0.99646643 1.38737559 1.75813075 1.32844540 0.53076589 0.96152349 1.31173062
> y
[1] 0 1 0 0 1 0 0 1 0 0 0 1 1 0 1 1 1 0 0 1
A more general solution is to use `ifelse` as it would allow you to use values other than zero and one:
> ifelse(x <= 1, -5, 5)
[1] -5 5 -5 -5 5 -5 -5 5 -5 -5 -5 5 5 -5 5 5 5 -5 -5 5
Finally, it is worth noting that you can use more complex expressions with either of the two approaches:
> ifelse(x >= .5 & x <= 1.5, -5, 5)
[1] 5 -5 5 5 -5 5 5 5 5 -5 -5 -5 5 -5 -5 5 -5 -5 -5 -5
Problem
Assuming I have a vector `x` containing 20 values between 0 and 2. ``` x = runif(20, 0, 2) ``` Now, I want to create another vector `y` (a binary variable) containing only 0 and 1 on the following condition: `y = 0` if `x < 1` and `y = 1` in case `x > 1`. I tried to do it with a loop and an `if` statement in the following way: ``` x = runif(20, 0, 2) # Create a vector of 20 values between 0 and 2 y = rep(5, 20) # Create a vector of 20 values (only 5's) for(i in 1:length(x)) # Loop that assigns values to the y vector depending on x { if(x < 1) { y[i] = 0 } else { y[i] = 1 } } ``` But it unfortunately did not work as planned as my `y` vector ends up containing 0's only. What did I do wrong? Thank you :)