Data objects

myVec <- 1:10; names(myVec) <- letters[1:10]  
myVec[1:5]

## a b c d e 
## 1 2 3 4 5

myVec[c(2,4,6,8)]

## b d f h 
## 2 4 6 8

myVec[c("b", "d", "f")]

## b d f 
## 2 4 6

factor(c("dog", "cat", "mouse", "dog", "dog", "cat"))

## [1] dog   cat   mouse dog   dog   cat  
## Levels: cat dog mouse

myMA <- matrix(1:30, 3, 10, byrow = TRUE) 
class(myMA)

## [1] "matrix"

myMA[1:2,]

##      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
## [1,]    1    2    3    4    5    6    7    8    9    10
## [2,]   11   12   13   14   15   16   17   18   19    20

myMA[1, , drop=FALSE]

##      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
## [1,]    1    2    3    4    5    6    7    8    9    10

myDF <- data.frame(Col1=1:10, Col2=10:1) 
myDF[1:2, ]

##   Col1 Col2
## 1    1   10
## 2    2    9

myL <- list(name="Fred", wife="Mary", no.children=3, child.ages=c(4,7,9)) 
myL

## $name
## [1] "Fred"
## 
## $wife
## [1] "Mary"
## 
## $no.children
## [1] 3
## 
## $child.ages
## [1] 4 7 9

myL[[4]][1:2] 

## [1] 4 7

myfct <- function(arg1, arg2, ...) { 
	function_body 
}

myVec <- 1:26; names(myVec) <- LETTERS 
myVec[1:4]

## A B C D 
## 1 2 3 4

myLog <- myVec > 10
myVec[myLog] 

##  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z 
## 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

myVec[c("B", "K", "M")]

##  B  K  M 
##  2 11 13

iris$Species[1:8]

## [1] setosa setosa setosa setosa setosa setosa setosa setosa
## Levels: setosa versicolor virginica