S Functions

S has built into it many standard mathematical and statistical functions.

Function   Value 

log(x)     the natural logarithm of each element of x 

logb(x,b)   the base b logarithm of each element of x

exp(x)     the exponential of each element of x, ie. e^x 

sqrt(x)    the square root of each value of x 

mean(x)	   the arithmetic average of the vector x
 
median(x)  the median value of x 

var(x)     the variance of x; 
             note:  the standard deviation of x is sqrt(var(x))

max(x)     the largest value in x 

min(x)     the smallest value in x 

range(x)   equivalent to c(min(x),max(x))

sum(x)     the sum of the elements in x 

rank(x)	   the relative rank of each element found in x 

sort(x)	   the values of x sorted into ascending order

There are numerous functions in S, including much more complicated ones such as the `lm()' function, which does linear regression calculations.

You can also create your own functions. For example:

> # create the function
> sd <- function(x){sqrt(var(x))}

> # print the function
> sd
function(x)
{
        sqrt(var(x))
}

> # use the function
> y <- 1:5
> sd(y)
[1] 1.581139