**Source Code of R Method**

There are different ways to view the source code of an R method or function. It will help to know how function is working.

**Internal Functions
**If you want to see the source code of internal function (functions from base packages), just type the name of the function at R prompt such as;

**Functions or Methods from S3 Class System
**For S3 classes,

*methods*function can be used to list the methods for a particular generic function or class.

> methods(predict)

Note that “Non-Visible functions are asterisked” means that the function is not exported from its package’s namespace.

One can still view its source code via the ::: function such as

> stats:::predict.lm

or by using *getAnywhere()* function, such as

> getAnywhere(predict.lm)

Note that the *getAnywhere()* function is useful as you don’t need to know from which package the function or method is came from.

**Functions or Methods from S4 Class System
**The S4 system is a newer method dispatch system and is an alternative to the S3 system. The package ‘Matrix’ is an example of S4 function.

> library(Matrix)

> chol2inv

The output already offers a lot of information. The *standardGeneric* is an indicator of an S4 function. The method to see defined S4 methods is to use showMethods(chol2inv), that is;

>showMethods(chol2inv)

The *getMethod* can be used to see the source code of one of the methods, such as,

> getMethod (“chol2inv”, “diagonalMatrix”)

**Functions that Calls Unexported Functions**

In the case of unexported functions such as *ts.union*, *.cbindts* and *.makeNamesTs* from the **stats** namespace, one can view source code of these unexported functions using ::: operator or *getAnywhere()* function, for example;

> stats::: .makeNamesTs

> getAnywhere(.makeNamesTs)

**View on Youtube**