Vectors and Simple Manipulations
This section introduces the basic operations on vectors, most of which are done element-wise. Please pay attention to the recycling of vectors (usually, recycling doesn't generate an error or a warning, so it is easy to miss if it was unintended), missing values (NA), and logical vectors often used for data subsetting.
Character vectors
Character quantities and character vectors are used frequently in R,
for example as plot labels. Where needed they are denoted by a sequence
of characters delimited by the double quote character, e.g.,
"x-values", "New iteration results".
Character strings are entered using either matching double (") or
single (') quotes, but are printed using double quotes (or
sometimes without quotes). They use C-style escape sequences, using
\ as the escape character, so \ is entered and printed as
\\, and inside double quotes " is entered as \".
Other useful escape sequences are \n, newline, \t, tab and
\b, backspace - see ?Quotes for a full list.
Character vectors may be concatenated into a vector by the c()
function; examples of their use will emerge frequently.
The paste() function takes an arbitrary number of arguments and
concatenates them one by one into character strings. Any numbers given
among the arguments are coerced into character strings in the evident
way, that is, in the same way they would be if they were printed. The
arguments are by default separated in the result by a single blank
character, but this can be changed by the named argument,
sep=string, which changes it to string,
possibly empty.
For example
> labs <- paste(c("X","Y"), 1:10, sep="")
makes labs into the character vector
c("X1", "Y2", "X3", "Y4", "X5", "Y6", "X7", "Y8", "X9", "Y10")
Note particularly that recycling of short lists takes place here too;
thus c("X", "Y") is repeated 5 times to match the sequence
1:10.