#Biostatistics 050

# PERMUTATIONS AND COMBINATIONS

n=20

k=7


#PERMUTATIONS

# No built-in function found, so I'll calculate it directly
Permutations=factorial(n)/(factorial(n-k))
Permutations

# COMBINATIONS - calculated directly

Combinations=factorial(n)/(factorial(k)*factorial(n-k))
Combinations

# BUILT-IN FUNCTION FOR COMBINATIONS
choose(n,k)

#VARIANCE AND COVARIANCE FUNCTIONS:

attach(iris)
SL=Sepal.Length
SW=Sepal.Width
PL=Petal.Length
PW=Petal.Width
detach(iris)

IR=cbind(SL,SW,PL,PW)
var(IR)
cov(IR)
var(iris)
cov(iris)