Book Image

R Object-oriented Programming

By : Kelly Black
Book Image

R Object-oriented Programming

By: Kelly Black

Overview of this book

Table of Contents (19 chapters)
R Object-oriented Programming
About the Author
About the Reviewers
Calculating Probabilities and Random Numbers
Package Management

Conditional execution

The first control construct examined is the if statement. An if statement will determine whether or not a code block should be executed, and it has an optional else statement. An additional if statement can be chained to an else statement to create a cascade of options.

In its most basic form, an if statement has the following form:

  code block

The condition can be a logical statement constructed from the operators given in the next table, or it can be a numeric result. If the condition is numeric, then zero is considered to be FALSE, otherwise the statement is TRUE. The code block can either be a single statement or a set of statements enclosed in braces:

> # check if 1 is less than 2
> if(1<2)
+    cat("one is smaller than two.\n")
one is smaller than two.
> if(2>1) {
+    cat("But two is bigger yet.\n")
+ }
But two is bigger yet.

Note that a comment is included in the previous code. The # character is used to denote a comment. Anything after...