Packages¶
Installing packages¶
R has a rich collection of packages. They allow researchers to share R functions and data. You can install packages available in the CRAN repository using install.packages. We already learned how we can get help
?install.packages
help("install.packages")
You can also install packages from the R Studio interface
For the next tasks you will need to install UsingR and MASS packages available in the CRAN repository.
install.packages("UsingR")
install.packages("MASS")
We can also install packages from GitHub using install_github. But first you need to install devtools from CRAN.
You can also see available packages using the available.packages or update a package using update.packages functions.
Loading packages¶
Just because a package is installed on your computer does not mean that you have access to its functions. We need to load the package into the current R session. Getting help
?library
library(UsingR)
library(MASS)
In R we have Warning and Error messages. Warning messages do not stop the flow of the function.
You can also use the require function to load a package.
Session info¶
You can see information about your current session - R version, OS, attached or loaded packages and their versions using sessionInfo.
sessionInfo()
Unloading packages¶
Sometimes you need to unload a package.
#| eval: false
detach("package:MASS")
Uninstalling packages¶
remove.packages remove installed packages.
#| eval: false
remove.packages("MASS")
Example¶
Next are considered examples with mtcars data frame from datasets package.
head(mtcars)
Wring ? before the name of the data frame gives information about the data frame, if it is available.
?mtcars
You can see what is this data frame about and some information about the data contained in the columns.
As we already saw we can use dim,nrow and ncol to show the dimensions of the data frame
dim(mtcars)
nrow(mtcars)
ncol(mtcars)
Next different ways to take only part of the data frame are reviewed. Shows the element in the 1 row, 2 column
mtcars[1, 2]
Shows the element in the “Mazda RX4” row, “cyl” column
mtcars["Mazda RX4", "cyl"]
Shows the elements in the 9 column
mtcars[[9]]
Shows the element in the “am” column
mtcars[["am"]]
Shows the element in the “am” column
mtcars$am
Attach data frame¶
Taking the names of the columns in the data frame
names(mtcars)
Let’s say we want to take the mpg column, we can use $ after the data frame’s name
mtcars$mpg
or to attach the data frame and only to write the name of the column.
attach(mtcars)
mpg
attach loads the data frame, so it is not necessary to write the data frame’s name in front of the column name. Getting help
?attach
Sometime this is very helpful, but it is important to notice that if you change the attached object the data frame is not going to change. For example let’s change the first value
mpg[1] = 200
mpg
mtcars$mpg