R environment commands

Which is the current working directory?

Firstly, to evaluate which is the current working directory (the one in which files are saved and the one that R reads) we use:

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getwd()

DO NOT type anything in the brackets.
It returns a string representing the path of the working directory. It could be useful to store it in a variable in order to easily use it in other functions.

How to change the working directory?

To change the current working directory, type:

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setwd("path")

Replace path with the desired one. To confirm that the wd is changed, use getwd().

Packages

Now, we’re going to see how to handle packages

Installed packages

There is a useful command to retrieve the list of installed packages; unfortunately it returns a character vector that is difficult to read. For this reason, int the following code there is an extra part that allows us to obtain only the name of the packages, their versions and their depends.

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installed.packages()[,c(3,5)]

To quickly evaluate if a package is present, we can use:

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"package" %in% installed.packages()[,1]

Install new package

If the required package is not in that list or if we know that it should be installed, we use:

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install.packages("packages")

To uninstall a package: uninstall.pachages("packages").
Packages inside brackets could be a single package or a vector of more packages.

Loaded packages

To retrieve which packages are active we use this command:

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(.packages())

It returns a character vector with all the active packages.
To quickly evaluate if a package is loaded, we can use:

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"package" %in% (.packages())

Load a package

If our package is not loaded and we want to load it, we have to type:

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library(pachages)

To unload a package:detach(package:pacchetto, unload = TRUE)

Environment

Let’s see how to handle environment variables.

Variable list

To retrieve which variables are stored:

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ls()

It returns a vactor with the names of the stored variables.

Remove variables

This is the function that removes variables:

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rm(variable)

Variable could be both the name of a variable or a list of variable (NOT a vector). So, in order to remove more variables we should use rm(list = c(variables)), and to remove all variables rm(list = ls()).

History

History is a fundamental element when we’re working on projects. For this reason, there are a couple of functions that we must know.

Save the history

Saving the history is useful when we are testing some codes, some functions or doing an analysis. To do it:

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savehistory("filename.Rhistory")

This file is stored in the current working directory, to change directory we shoul insert the path in the filename.

load the history

To load the history from a saved file:

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loadhistory("filename.Rhistory")