Basics

Vector (aka mother of all data structures)

# Skalar?
x <- 5

# First element
x[1]

## [1] 5

# Everything is an object
class(x)

## [1] "numeric"

nm <- c("Peter", "Bender")
nr <- c(2, 4)

paste("Hi", nm, "your id is", nr)

## [1] "Hi Peter your id is 2"  "Hi Bender your id is 4"

data frame (aka workhorse)

head(mtcars)

##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

# df[rows, columns]
mtcars[mtcars$gear == 4, c("cyl", "gear")]

##                cyl gear
## Mazda RX4        6    4
## Mazda RX4 Wag    6    4
## Datsun 710       4    4
## Merc 240D        4    4
## Merc 230         4    4
## Merc 280         6    4
## Merc 280C        6    4
## Fiat 128         4    4
## Honda Civic      4    4
## Toyota Corolla   4    4
## Fiat X1-9        4    4
## Volvo 142E       4    4

apply family or how to loop

# extraordinary
l <- list()
for(i in 1:4){
  l[[i]] <- sqrt(i)
}
l

## [[1]]
## [1] 1
## 
## [[2]]
## [1] 1.414214
## 
## [[3]]
## [1] 1.732051
## 
## [[4]]
## [1] 2

# apply family
l <- lapply(1:4, sqrt)
l

## [[1]]
## [1] 1
## 
## [[2]]
## [1] 1.414214
## 
## [[3]]
## [1] 1.732051
## 
## [[4]]
## [1] 2