bquote
Partial Substitution in Expressions

### Description

Returns a quoted expression, where the parts of the expression wrapped in .() are evaluated in the environment specified by the where argument.

### Usage

    bquote(expr, where = parent.frame(), splice = FALSE)

### Arguments

expr | an expression. Can include terms wrapped in .() indicating that the enclosed term should be evaluated. If this argument is missing, the missing value symbol itself is returned.
where | an integer specifying a frame, an environment, or a list of named elements defining the names occurring in the expression. This argument is similar to the envir argument in the function eval.
splice | a logical value. If TRUE, then calls of the form ..(a1) in a call in expr can change the number of arguments in the call. All the values in the evaluation of a1 are interpolated into the call containing the call to ..(a1). If FALSE (the default), then only calls of the form .(a1) are processed. Calls to ..() should occur only in calls.

### Details

bquote is similar in function to the LISP macro backquote.
Value
returns an expression similar to the input expression, but with all terms wrapped in .() replaced by their values.
Side Effects
Expressions that are wrapped in .() (or ..(), if splice is TRUE) are evaluated and can have side effects.
See Also
eval, quote, substitute.
Examples

    a <- 1
    bquote(log(.(a)) == .(log(a)))
    bquote(log(.(a)) == .(log(a)), list(a = exp(1)))
    bquote(y ~ .(f)(x), list(f = as.name("log")))
    bquote(func(.(x), ..(extras)), list(x=quote(log(ex)), extras=expression(1+2, 3/4)), splice=TRUE)
    bquote(func(.(x), .(extras)), list(x=quote(log(ex)), extras=expression(1+2, 3/4)), splice=FALSE)

Package base version 6.1.5-18
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