R Quotes In String

Posted on3/24/2022by admin

Lets create a sample string a string' A reminder before we proceed: Strings in R imply a character vector. If you recall the lowest datastructure in R is a vector. So a String is a character vector of length 1. You can do this: a1 1 'This is a sample string' the print function can be used to print the argument. Like strings, regexps use the backslash, to escape special behaviour. So to match an., you need the regexp. Unfortunately this creates a problem. We use strings to represent regular expressions, and is also used as an escape symbol in strings. So to create the regular expression. We need the string '.'

substitute {base}

R Documentation

Substituting and Quoting Expressions

Description

substitute returns the parse tree for the (unevaluated)expression expr, substituting any variables bound inenv.

quote simply returns its argument. The argument is not evaluatedand can be any R expression.

enquote is a simple one-line utility which transforms a call ofthe form Foo(....) into the call quote(Foo(....)). Thisis typically used to protect a call from early evaluation.

The print method (print.noquote) prints character strings without quotes (' dots'). If right is specified in a call print(x, right=.), it takes precedence over a possible right setting of x, e.g., created by x. String is surrounded in double quotes, which suppresses all special meanings of metacharacters except dollar, backquote and backslash, so these (and of course double quote) are preceded by backslash. This type of quoting is also appropriate for bash, kshand.

Usage

Arguments

`expr`	any syntactically valid R expression
`cl`	a `call`, i.e., an R object of`class` (and `mode`) `'call'`.
`env`	an environment or a list object. Defaults to thecurrent evaluation environment.

Details

The typical use of substitute is to create informative labelsfor data sets and plots.The myplot example below shows a simple use of this facility.It uses the functions deparse and substituteto create labels for a plot which are character string versionsof the actual arguments to the function myplot.

Substitution takes place by examining each component of the parse treeas follows: If it is not a bound symbol in env, it isunchanged. If it is a promise object, i.e., a formal argument to afunction or explicitly created using delayedAssign(),the expression slot of the promise replaces the symbol. If it is anordinary variable, its value is substituted, unless env is.GlobalEnv in which case the symbol is left unchanged.

Both quote and substitute are ‘special’primitive functions which do not evaluate their arguments.

Value

The mode of the result is generally 'call' butmay in principle be any type. In particular, single-variableexpressions have mode 'name' and constants have theappropriate base mode.

Note

substitute works on a purely lexical basis. There is noguarantee that the resulting expression makes any sense.

Substituting and quoting often cause confusion when the argument isexpression(...). The result is a call to theexpression constructor function and needs to be evaluatedwith eval to give the actual expression object.