The Art of R Programming

Here, we found two objects whose names include the string"notebook"

and then asked to remove them, which was confirmed by the second call

tols().

NOTE You may find the functionbrowseEnv()helpful. It will show in your web browser your

globals (or objects in a different specified environment), with some details on each.

9.4.3 Saving a Collection of Objects with the save() Function.............

Callingsave()on a collection of objects will write them to disk for later

retrieval byload(). Here’s a quick example:

> z <- rnorm(100000)

> hz <- hist(z)

> save(hz,"hzfile")

> ls()

[1] "hz" "z"

> rm(hz)

> ls()

[1] "z"

> load("hzfile")

> ls()

[1] "hz" "z"

> plot(hz) # graph window pops up

Here, we generate some data and then draw a histogram of it. But

we also save the output ofhist()in a variable,hz. That variable is an object

(of class"histogram", of course). Anticipating that we will want to reuse this

object in a later R session, we use thesave()function to save the object to

the filehzfile. It can be reloaded in that future session viaload(). To demon-

strate this, we deliberately removed thehzobject, then calledload()to reload

it, and then calledls()to show that it had indeed been reloaded.

I once needed to read in a very large data file, each record of which

required processing. I then usedsave()to keep the R object version of the

processed file for future R sessions.

9.4.4 “What Is This?”.................................................

Developers often need to know the exact structure of the object returned by

a library function. If the documentation does not give sufficient details, what

can we do?

The following R functions may be helpful:

• class(),mode()


• names(),attributes()


• unclass(),str()


• edit()

228 Chapter 9