Creating a random sequence using sample() in R

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It is not uncommon to generate random sequences in R programming. sample() function provides the feasibility of generating such random objects from given vectors, either with or without replacement. The following code shows an example that 32 numbers with replacement drawn from 50 integers from 1 to 50.

#random sequence drawn with replacement from given vector
vec_replace <- sample(1 : 50, size = 32, replace = T)  

vec_replace

#output
[1]  1  3 48 20 14 37 39 42 34  9 43 14  6 18 32 28 32 32 39 44 33  9 40 2 41 43 21 50 14 32 25  3

Alternatively, random sequence can be drawn without replacement, which is shown in the following code.

#random sequence drawn without replacement from given vector
vec__no_replace <- sample(1 : 50, size = 32, replace = F)  

vec__no_replace
#output
[1] 48 10 16 33  3  9  1 49 34 32 36 37 29  7 44 24 41 11 23 39 19 20 21 27 50 42 47 15 40 17  8 14

sample() function provides also the option to specify the expected probability associated with each seed element, such that the generated sequence complies with this specified ratio. The next example code shows 1000 random numbers drawn from 5 integers from 3 to 7, with the probability specified for each number.

#random sequence drawn with specified probabilities
vec_prob <- sample(3:7, size = 1000, replace = T,
       prob = c(0.1, 0.2, 0.15, 0.25, 0.3))

vec_prob
#output
  [1] 3 3 4 6 4 7 5 6 5 7 3 7 6 7 5 6 7 6 6 6 3 6 6 5 6 6 5 7 4 5 5 5 6 5 7 6 7 4 3 4 6 5 7 
,,, 
[953] 4 4 7 7 5 5 6 7 6 4 6 6 5 4 5 7 4 6 6 6 7 5 3 6 6 7 7 5 6 6 7 6 6 4
 [987] 6 7 6 7 7 7 7 5 5 7 5 7 6 6

table(vec_prob)/1000*100

  #output , the frequency is close to the specified #probabilities
 3    4    5    6    7 
 9.5 20.5 15.2 26.0 28.8 

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