How to install packages

if you run into the following problem:
> library ("arm")
Erreur dans library("arm") : aucun package nommé 'arm' n'est trouvé
(or a similar message in English)

it's probably because you have not installed the "arm" package yet.

To do so, open R and use the GUI (Graphical User Interface) as follows:
- click on the "Packages" menu
- select "choose mirror"
- select one in France
- click on the "Packages" menu again
- select "install packages"
- select "arm"

If you have any trouble with the GUI, you can directly type in the R console:
> chooseCRANmirror()
(R is case sensitive! -- meaning upper case letters are not interpreted the same way as lower case letters)

then type:
> install.packages()
then select "arm"

or directly, type:
> install.packages("arm")