使用if-else的R中的For-Loop：如何保存输出

Question

I am trying to save the output of the code below. I know "print" is the problem, but I do not know what works instead.

I generally wonder if there is not another way instead of the for-loop: For each value in the vector (x), I want to draw a new random number (here with runif) and match it to a given value (here for example 0.5). Depending on the result, a new value for x should be stored in a vector x2 (similar to the if-else example below). Waiving the for-loop, I could not find a way to always draw a new random number for each value in vector x. I would be very grateful for any help!

x <- c(2,2,2,3,3,3)

for(i in x){
  if(runif(1) <= 0.5){
    print(i + 1)
  } else {
    print(i)
  }
}

Answer 1

Or you could use lapply , then you don't have to modify an object outside your loop each step.

x <- c(2,2,2,3,3,3)

x2 <- unlist(lapply(x, function(x){
          if(runif(1) <= 0.5) return(x +1)
          return(x)
}))

x2

Answer 2

Try this code:

x <- c(2,2,2,3,3,3)
x2<-NULL

for(i in 1:length(x)){
   if(runif(1) <= 0.5){
     x2[i]<-1
   } else {
     x2[i]<-2
   }
 }

Your output

x2
[1] 1 2 2 1 2 1

In x2 you have random numbers with given values (1 and 2) related to the runif probability.

This is the same thing in a single row:

ifelse(runif(n = length(x))<=0.5,1,2)
[1] 1 2 2 2 1 1