| % File src/library/datasets/man/cars.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2007 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{cars} |
| \docType{data} |
| \alias{cars} |
| \title{Speed and Stopping Distances of Cars} |
| \description{ |
| The data give the speed of cars and the distances taken to stop. |
| Note that the data were recorded in the 1920s. |
| } |
| \usage{cars} |
| \format{ |
| A data frame with 50 observations on 2 variables. |
| \tabular{rlll}{ |
| [,1] \tab speed \tab numeric \tab Speed (mph)\cr |
| [,2] \tab dist \tab numeric \tab Stopping distance (ft) |
| } |
| } |
| \source{ |
| Ezekiel, M. (1930) |
| \emph{Methods of Correlation Analysis}. |
| Wiley. |
| } |
| \references{ |
| McNeil, D. R. (1977) |
| \emph{Interactive Data Analysis}. |
| Wiley. |
| } |
| \examples{ |
| require(stats); require(graphics) |
| plot(cars, xlab = "Speed (mph)", ylab = "Stopping distance (ft)", |
| las = 1) |
| lines(lowess(cars$speed, cars$dist, f = 2/3, iter = 3), col = "red") |
| title(main = "cars data") |
| plot(cars, xlab = "Speed (mph)", ylab = "Stopping distance (ft)", |
| las = 1, log = "xy") |
| title(main = "cars data (logarithmic scales)") |
| lines(lowess(cars$speed, cars$dist, f = 2/3, iter = 3), col = "red") |
| summary(fm1 <- lm(log(dist) ~ log(speed), data = cars)) |
| opar <- par(mfrow = c(2, 2), oma = c(0, 0, 1.1, 0), |
| mar = c(4.1, 4.1, 2.1, 1.1)) |
| plot(fm1) |
| par(opar) |
| |
| ## An example of polynomial regression |
| plot(cars, xlab = "Speed (mph)", ylab = "Stopping distance (ft)", |
| las = 1, xlim = c(0, 25)) |
| d <- seq(0, 25, length.out = 200) |
| for(degree in 1:4) { |
| fm <- lm(dist ~ poly(speed, degree), data = cars) |
| assign(paste("cars", degree, sep = "."), fm) |
| lines(d, predict(fm, data.frame(speed = d)), col = degree) |
| } |
| anova(cars.1, cars.2, cars.3, cars.4) |
| } |
| \keyword{datasets} |