Machine Learning with R Cookbook - Second Edition

How to do it...

Perform the following steps to measure the performance of the regression model:

1. Load the Quartet dataset from the car package:

        > library(car)
        > data(Quartet)

2. Plot the attribute, y3, against x using the lm function:

        > plot(Quartet$x, Quartet$y3)
        > lmfit = lm(Quartet$y3~Quartet$x)
        > abline(lmfit, col="red")  

The linear regression plot

3. You can retrieve predicted values by using the predict function:

        > predicted= predict(lmfit, newdata=Quartet[c("x")])  

4. Now, you can calculate the root mean square error:

        > actual = Quartet$y3
        > rmse = (mean((predicted - actual)^2))^0.5
        > rmse
        Output
        [1] 1.118286  

5. You can calculate the ...