CODEWITHSUNDEEP
rrandom
user3680912
user3680912

Reputation: 3

New variable with uniform random number bounded by constant and second variable value

I am trying to create a random number that is between 3 and a number provided by a column max.

Create a sample data frame for reproduction.

ID <- c(1:10)
max <- c(5,3,7,6,10,4,3,3,5,6)
df <- data.frame(ID,max)

I want a third column that is a random number between 3 and max.

  ID max
  1   5
  2   3
  3   7
  4   6
  5  10
  6   4
  7   3
  8   3
  9   5
 10   6

I have tried many variations of the following.

for(i in 1:nrow(df)){
df$rand[i] <- sample((3:df$max[i]),1,replace=TRUE)
}

The problem is the random numbers are not with in the bounds of 3 and max. See row 8. I set my seed to 1234. 

   ID max rand
1   1   5    3
2   2   3    3
3   3   7    4
4   4   6    4
5   5  10    5
6   6   4    4
7   7   2    3
8   8   3    2
9   9   5    4
10 10   6    3

Thanks for any help here. I am still learning R and struggling with code.

Upvotes: 0

Views: 89

Answers (3)

David Arenburg
David Arenburg

Reputation: 92282

You could also keep using sample just with some constrains (and avoid using floor or round)

df$rand <- sapply(seq_len(dim(df)[1]), function(x) if(df$max[x] > 3) sample(3:df$max[x], 1, replace = T) else 3)

##   ID max rand
##1   1   5    3
##2   2   3    3
##3   3   7    6
##4   4   6    5
##5   5  10    7
##6   6   4    4
##7   7   2    3
##8   8   3    3
##9   9   5    4
##10 10   6    3

Upvotes: 0

agstudy
agstudy

Reputation: 121568

Another option using transform and take care of the case where the max < 3:

 transform(dat,y = sapply(max,function(x)floor(runif(1,3,if(x>3)x else 3))))

  ID max y
1   1   5 4
2   2   3 3
3   3   7 6
4   4   6 4
5   5  10 9
6   6   4 3
7   7   2 3
8   8   3 3
9   9   5 3
10 10   6 3

Upvotes: 0

Robert Krzyzanowski
Robert Krzyzanowski

Reputation: 9344

df$rand <- sapply(df$max, function(max) round(runif(1, 3, max)))

Your 7th row has max = 2 which is why we get a NaN. 

ID max rand
1   1   5    4
2   2   3    3
3   3   7    4
4   4   6    4
5   5  10    3
6   6   4    4
7   7   2  NaN
8   8   3    3
9   9   5    4
10 10   6    4

Upvotes: 1

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