10.2 Random number
To generate random integers, we use the function sample().
We first generate 8 random integers between 2 and 10 without replacement:
sample(2:10,8, replace=F)
## [1] 5 2 10 9 7 4 8 3
The next one generate 7 integers between 2 and 10 with replacement:
sample(2:10,7, replace=T)
## [1] 10 8 9 5 5 5 2
In general, the sample() function can also be applied to extract random element from a vector.
namelist<-c("Mary", "Peter", "John", "Susan")
sample(namelist,2) # sample from this list
## [1] "John" "Peter"
To generate random decimal numbers, we use runif to get random uniform distribution. The following generates 2 random decimal numbers between 4.6 and 7.8:
runif(2, 4.6, 7.8)
## [1] 5.644185 6.294448
To generate normal distribution, we use rnorm(). The following generate 4 random number that follows the normal distribution with mean being 0 and standard deviation being 1.
x <- rnorm(4, mean=0, sd=1) # standard nromal
x
## [1] -1.5259096 1.5450039 1.1077966 0.3269604