R Object-oriented Programming

The function takes at least three arguments. The first is the data to apply an operation, the second is the set of factors that defines how the data is organized with respect to the different levels, and the third is the operation to perform.

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:

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

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

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

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:

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

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.

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.