R For loop replace previsouly assigned values

user_14535027 0
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I'd like to use uniform distribution to randomly assign value 1 or 2 for five groups(generate 5 random uniform distribution), with each group containing 10 samples.

I try to write:

for(i in 1:5){
        rf <- runif(10)
      result[rf<=0.5]=1
      result[rf>0.5]=2
      }

However this will replace the previously assigned values when the loop goes on. The code produces only 10 results:

1 2 1 2 2 1 1 1 2 1

But I want a total of 50 randomized values:

1 2 1 2 ...... 2 1 1

How to do this? Thank you

r for-loop
2 Answers

Since, you are working on random number generated from same distribution every time, you can better generate 50 numbers in once, and assign value using ifelse function.

Try this:

a <- ifelse(runif(50) <= 0.5, 1, 2)
dim(a) <- c(10,5) #if result in matrix
user_50473110

To add to Gregor Thomas' advice, sample... You can also covert the stream into a matrix of 5 columns (groups) of 10.

nums <- sample(1:2, 50, replace = TRUE)
groups <- matrix(nums, ncol = 5)
user_35741560
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