The Art of R Programming

Don’t worry about the details ofprint.lm(). The main point is that the

printing depends on context, with a special print function called for the

"lm"class. Now let’s see what happens when we print this object with its

class attribute removed:

> unclass(lmout)

$coefficients

(Intercept) x

-3.0 3.5

$residuals

123

0.5 -1.0 0.5

$effects

(Intercept) x

-6.928203 -4.949747 1.224745

$rank

[1] 2

I’ve shown only the first few lines here—there’s a lot more. (Try run-

ning this on your own!) But you can see that the author oflm()decided

to makeprint.lm()much more concise, limiting it to printing a few key

quantities.

9.1.3 Finding the Implementations of Generic Methods...................

You can find all the implementations of a given generic method by calling

methods(), like this:

> methods(print)

[1] print.acf*

[2] print.anova

[3] print.aov*

[4] print.aovlist*

[5] print.ar*

[6] print.Arima*

[7] print.arima0*

[8] print.AsIs

[9] print.aspell*

[10] print.Bibtex*

[11] print.browseVignettes*

[12] print.by

[13] print.check_code_usage_in_package*

[14] print.check_demo_index*

[15] print.checkDocFiles*

210 Chapter 9