Residual Plot
The residual data of the simple linear regression model is the difference between the observed data of the dependent variable y and the fitted values ŷ.
Problem
Plot the residual of the simple linear regression model of the data set faithful against the independent variable waiting.
Solution
We apply the lm function to a formula that describes the variable eruptions by the variable waiting, and save the linear regression model in a new variable eruption.lm. Then we compute the residual with the resid function.
We now plot the residual against the observed values of the variable waiting.
> plot(faithful$waiting, eruption.res,
+ ylab="Residuals", xlab="Waiting Time",
+ main="Old Faithful Eruptions")
> abline(0, 0) # the horizon
+ ylab="Residuals", xlab="Waiting Time",
+ main="Old Faithful Eruptions")
> abline(0, 0) # the horizon
Note
Further detail of the resid function can be found in the R documentation.
