Learn R – 3 Commands to Generate Random Numbers

This article represents 3 different commands with code examples which could be used to generate random numbers in R programming language. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

• Runif command
• Sample command
• Rnorm command
• Difference between runif and rnorm command

Runif: Generate Random Numbers based on Uniform Distribution

“Runif” command can be used for generating random numbers based on uniform distribution. One can generate one or more random numbers within a range of numbers. One should note that the random numbers generated using runif commands are all decimal (non-integers) numbers.

# Generate 5 random numbers
runif(5)

# Generate 5 random numbers (Non-integers) between 2 and 7
runif(5, 2, 7)

Sample: Generate Random Numbers based on Uniform Distribution

“Sample” command is also used for generating random numbers based on uniform distribution. One can generate one or more random numbers within a range of numbers. One should note that the random numbers generated using runif commands are all integer numbers. This is the key difference between runif and sample command.

# Generate 5 random numbers (Integers)
sample(5)

# Generate 5 random numbers (Integers) between 2 and 7; Duplicates are allowed
# with replace parameter set to True (T)
sample(2:7, 5, replace=T)

# Generate 5 random numbers (Integers) between 2 and 7; Duplicates are NOT allowed
# with replace parameter set to False (F)
sample(2:7, 5, replace=F)

# Generate 5 country names from the vector countryNames with replace as false
countryNames <- c("India","USA","Pakistan","China","Japan","South Korea","Mangolia")
sample(countryNames, 5)

Rnorm: Generate Random Numbers based on Normal Distribution

“Rnorm” command is used for generating random numbers based on normal distribution.

# Generate 5 random numbers with mean as 0 and standard deviation as 1
rnorm(5)

# Generate 5 random numbers with mean as 5 and standard deviation as 2
rnorm(500, mean=5, sd=2)

Random Number Generation for Uniform & Normal Distribution

The key difference between runif/sample and rnorm command is following:

• runif/sample command generates the random numbers based on uniform distribution
• rnorm command generates random numbers based on normal distribution