Thus it is important to remember which logical operator to use in which situation. Whereas & (and) and | (or) apply element-wise to vectors, & and || apply to vectors of length one, and only evaluate their second argument in the sequence if necessary. The operators & and || are often used to denote multiple conditions in an if statement. The above expression reads: if condition on the data is true, then do the true value assigned otherwise execute the 'false value.' Ifelse(condition on data, true value returned, false returned) In R, one can write a conditional statement as follows: That is a bit abstract, so let's get our hands dirty. Commands may be grouped together in braces,, in which case the value of the group is the result of the last expression in the group evaluated.

Even an assignment is an expression whose result is the value assigned, and it may be used wherever any expression may be used in particular multiple assignments are possible. R is an expression language in the sense that its only command type is a function or expression which returns a result. In this section we will explore some simple, yet powerful, programming tools in R, such as loops, if-then and while statements. One of the most powerful features of R is in being able to do programming, without a lot of the low-level detailed bookkeeping issues that one needs to keep track of in other computer programming languages like C, Java, Perl, etc. So far we have mainly used R for performing one-line commands on vectors or matrices of data. Programming Loops and If-then/for/while Statements

Creating a loop in r