How to get help in R?

Question

What is the possible documentation available for R package? For example I try to understand `sp` package. In addition to `help(sp)`, what are the other functions for searching through help and documentation?

Accepted Answer

Getting help on a function that you know the name of

Use `?` or, equivalently, `help`.

```
?mean
help(mean) # same
```

For non-standard names use quotes or backquotes; see An Introduction to R: Getting help with functions and features:

For a feature specified by special characters, the argument must be enclosed in double or single quotes, making it a “character string”: This is also necessary for a few words with syntactic meaning including `if`, `for` and `function`."

```
?`if`
?"if"       # same
help("if")  # same
```

There are also help pages for datasets, general topics and some packages.

```
?iris
?Syntax
?lubridate    
```

Use the `example` function to see examples of how to use it.

```
example(paste)
example(`for`)
```

The `demo` function gives longer demonstrations of how to use a function.

```
demo()                           # all demos in loaded pkgs
demo(package = .packages(all.available = TRUE)) # all demos
demo(plotmath)
demo(graphics)
```

Finding a function that you don't know the name of

Use `??` or, equivalently, `help.search`.

```
??regression
help.search("regression")
```

Again, non-standard names and phrases need to be quoted.

```
??"logistic regression"
```

`apropos` finds functions and variables in the current session-space (but not in installed but not-loaded packages) that match a regular expression.

```
apropos("z$") # all fns ending with "z"
```

`rseek.org` is an R search engine with a Firefox plugin.

`RSiteSearch` searches several sites directly from R.

`findFn` in `sos` wraps `RSiteSearch` returning the results as a HTML table.

```
RSiteSearch("logistic regression")

library(sos)
findFn("logistic regression")
```

Finding packages

`available.packages` tells you all the packages that are available in the repositories that you set via `setRepositories`. `installed.packages` tells you all the packages that you have installed in all the libraries specified in `.libPaths`. `library` (without any arguments) is similar, returning the names and tag-line of installed packages.

```
View(available.packages())
View(installed.packages())
library()
.libPaths()
```

Similarly, `data` with no arguments tells you which datasets are available on your machine.

```
data()
```

`search` tells you which packages have been loaded.

```
search()
```

`packageDescription` shows you the contents of a package's `DESCRIPTION` file. Likewise `news` read the `NEWS` file.

```
packageDescription("utils")    
news(package = "ggplot2")
```

Getting help on variables

`ls` lists the variables in an environment.

```
ls()                 # global environment
ls(all.names = TRUE) # including names beginning with '.'
ls("package:sp")     # everything for the sp package
```

Most variables can be inspected using `str` or `summary`.

```
str(sleep)
summary(sleep)
```

`ls.str` is like a combination of `ls` and `str`.

```
ls.str()
ls.str("package:grDevices")
lsf.str("package:grDevices")  # only functions    
```

For large variables (particularly data frames), the `head` function is useful for displaying the first few rows.

```
head(sleep)
```

`args` shows you the arguments for a function.

```
args(read.csv)
```

General learning about R

The Info page is a very comprehensive set of links to free R resources.

Many topics in R are documented via `vignette`s, listed with `browseVignettes`.

```
browseVignettes()
vignette("intro_sp", package = "sp")
```

By combining `vignette` with `edit`, you can get its code chunks in an editor.

```
edit(vignette("intro_sp",package="sp"))    
```

How to get help in R?

Solution

Problem