Basics about data structures and subsetting

Created on the fly

We consider

• subsetting
• dataframes body fat data

library(ggplot2)
age    <- c(23, 28, 38, 44, 50, 53, 57, 59, 60)
fatpct <- c(19.2, 16.6, 32.5, 29.1, 32.8, 42, 32, 34.6, 40.5)

Various subsettings on vectors

qplot(age, fatpct)

age2    <- age[c(5,6,7,8,9)]
age2  

## [1] 50 53 57 59 60

age2 <- age[age >= 50]

fatpct2 <- fatpct[age >= 50]
fatpct2

## [1] 32.8 42.0 32.0 34.6 40.5

age2 <- age[age >= 50 & age <= 55]
age2

## [1] 50 53

age2 <- age[!(age >= 50)]
age2

## [1] 23 28 38 44

Creating dataframes

agefat <- data.frame(a=age, f=fatpct)
agefat

##    a    f
## 1 23 19.2
## 2 28 16.6
## 3 38 32.5
## 4 44 29.1
## 5 50 32.8
## 6 53 42.0
## 7 57 32.0
## 8 59 34.6
## 9 60 40.5

agefat[1:5, ]

##    a    f
## 1 23 19.2
## 2 28 16.6
## 3 38 32.5
## 4 44 29.1
## 5 50 32.8

Where to find data

cars

##    speed dist
## 1      4    2
## 2      4   10
## 3      7    4
## 4      7   22
## 5      8   16
## 6      9   10
## 7     10   18
## 8     10   26
## 9     10   34
## 10    11   17
## 11    11   28
## 12    12   14
## 13    12   20
## 14    12   24
## 15    12   28
## 16    13   26
## 17    13   34
## 18    13   34
## 19    13   46
## 20    14   26
## 21    14   36
## 22    14   60
## 23    14   80
## 24    15   20
## 25    15   26
## 26    15   54
## 27    16   32
## 28    16   40
## 29    17   32
## 30    17   40
## 31    17   50
## 32    18   42
## 33    18   56
## 34    18   76
## 35    18   84
## 36    19   36
## 37    19   46
## 38    19   68
## 39    20   32
## 40    20   48
## 41    20   52
## 42    20   56
## 43    20   64
## 44    22   66
## 45    23   54
## 46    24   70
## 47    24   92
## 48    24   93
## 49    24  120
## 50    25   85

qplot(speed, dist, data=cars)

speed <- cars$speed
dist  <- cars$dist
qplot(speed, dist)

rm(speed, dist)

with(cars, qplot(speed, dist))