Kelly Black

The <- operator for the assignment will work in any context while the = operator only works for complete expressions. Another option is to use the <<- operator. The advantage of the <<- operator is that it instructs the R environment to search parent environments to see whether the variable already exists.

In some contexts, within a function for example, the <- operator will create a new variable; however, the <<- operator will make use of an existing variable outside of the function if it is found.

Here, we briefly list some of the built-in data types that describe discrete data. The four data types discussed are the integer, logical, character, and factor data types.

We also introduce the idea of a vector, which is the default data structure for any variable.

Note that there is a difference between operations such as & and &&. A single & is used to perform an and operation on each pairwise element of two vectors, while the double && returns a single logical result using only the first elements of the vectors:

The names used to assign variables are just a shortcut for R to determine where an object is located.

Vectors represent a convenient and straightforward way to store a long list of numbers.

The : notation is used to create a list of sequentially numbered values for given start and end values.

The rows and columns of the table have names associated with them, and the rownames and colnames commands can be used to assign the names. These commands are similar to the names command.

The apply command is used to apply a given function across a given margin of an array or table. For example, to take the sum of a row or column from a two way table, use the apply command with arguments for the table, the sum command, and which dimension to use: