6 Datasets in R
There are various pre-built data sets included with R, which are typically used as practice sets for playing with R functions. We’ll first go through how to load and use built-in R data sets in this lecture. The most popular R demo data sets will then be discussed, including mtcars, iris, ToothGrowth, PlantGrowth, and USArrests.
6.1 Pre-loaded data
To see the list of pre-loaded data in your system, type the function data():
data()6.2 Loading a built-in R data
Load and print mtcars data as follow:
## 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 16.3 Most used data sets in R
6.3.1 mtcars
mtcars data was extracted from the 1974 Motor Trend US magazine, and comprises fuel consumption and 10 aspects of automobile design and performance for 32 automobiles (1973–74 models).
## 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
# Number of rows (observations)
nrow(mtcars) ## [1] 32
# Number of columns (variables)
ncol(mtcars)## [1] 11If you want learn more about mtcars data sets, type this: ?mtcars
?mtcars6.3.2 iris
iris data set gives the measurements in centimeters of the variables sepal length, sepal width, petal length and petal width, respectively, for 50 flowers from each of 3 species of iris. The species are Iris setosa, versicolor, and virginica.
## Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1 5.1 3.5 1.4 0.2 setosa
## 2 4.9 3.0 1.4 0.2 setosa
## 3 4.7 3.2 1.3 0.2 setosa
## 4 4.6 3.1 1.5 0.2 setosa
## 5 5.0 3.6 1.4 0.2 setosa
## 6 5.4 3.9 1.7 0.4 setosaIf you want learn more about iris data sets, type this: ?iris
?iris6.3.3 ToothGrowth
The results of an experiment examining the impact of vitamin C on tooth development in 60 Guinea pigs are included in the data set. Each rat received one of three vitamin C dose levels (0.5, 1, and 2 mg/day) using either ascorbic acid or orange juice as the delivery mechanism (a form of vitamin C and coded as VC).
## len supp dose
## 1 4.2 VC 0.5
## 2 11.5 VC 0.5
## 3 7.3 VC 0.5
## 4 5.8 VC 0.5
## 5 6.4 VC 0.5
## 6 10.0 VC 0.5If you want learn more about ToothGrowth data sets, type this: ?ToothGrowth
?ToothGrowth6.3.4 PlantGrowth
Results from an experiment comparing yields between two distinct treatment conditions and a control condition (as determined by the dry weight of plants).
## weight group
## 1 4.17 ctrl
## 2 5.58 ctrl
## 3 5.18 ctrl
## 4 6.11 ctrl
## 5 4.50 ctrl
## 6 4.61 ctrl