2 R basics

2.1 Basic operations

> 2 + 2
## [1] 4
> 
> 7 * 17
## [1] 119
> 
> sqrt(9)
## [1] 3
> 
> 3^3
## [1] 27
> 
> log(7)
## [1] 1.94591
> 
> log10(7)
## [1] 0.845098

2.2 Precision

> sin(pi/2)
## [1] 1
> 
> pi
## [1] 3.141593
> 
> options(digits = 22)
> 
> pi
## [1] 3.141592653589793115998
> 
> options(digits = 4)

2.3 Infinity or not defined, and missings

> 1/0
## [1] Inf
> 
> 2 * Inf
## [1] Inf
> 
> -1/0
## [1] -Inf
> 
> 0/0
## [1] NaN
> 
> c(1, 2, 3, NA, 5)
## [1]  1  2  3 NA  5
> 
> mean(c(1, 2, 3, NA, 5))
## [1] NA
> 
> mean(c(1, 2, 3, 5))
## [1] 2.75

2.4 Important commands

> ls()  #...display list of variables in memory
> 
> ls.str()  #...display the structure os the list of variables in memory
> 
> rm(a)  #...remove an object
> 
> rm(list = ls())  #...remove ALL objects
> 

2.5 Internal help function

> help(mean)  # shorthand for help(mean)

> example(mean)  # examples

> help.search("mean")  # full information

> help.start()  # manuals