max() function computes the maximun value of a vector. min() function computes the minimum value of a vector.

max(x,na.rm=FALSE)
min(x,na.rm=FALSE)

• x: number vector
• na.rm: whether NA should be removed, if not, NA will be returned

> x <- c(1,2.3,2,3,4,8,12,43,-4,-1)
> max(x)

[1] 43

> min(x)

[1] -4

Missing value affect the results:

> y<- c(x,NA)
> y

[1] 1.0 2.3 2.0 3.0 4.0 8.0 12.0 43.0 -4.0 -1.0 NA

> max(y)

[1] NA

> min(y)

[1] NA

After define na.rm=TRUE, result is meaningful:

> max(y,na.rm=TRUE)

[1] 43

Compare more than 1 vectors:

> x2 <- c(-100,-43,0,3,1,-3)
> min(x,x2)

[1] -100

apply() function can be used to calculate the max/min of each row and column of a matrix:

> A <- matrix(c(3,5,7,1,9,4),nrow=3,ncol=2,
dimnames=list(c("a","b","c"),c("x","y")))
> A
  x y
a 3 1
b 5 9
c 7 4
> apply(A, 1, max) #1 is for row
a b c
3 9 7
> apply(A, 2, max) #2 is for column
x y
7 9
> max.col(A)
[1] 1 2 1