within.qenv | R Documentation |
qenv
Evaluate code in qenv
## S3 method for class 'qenv'
within(data, expr, ...)
data |
( |
expr |
( |
... |
named argument value will substitute a symbol in the |
within()
is a convenience method that wraps eval_code
to provide a simplified way of passing expression.
within
accepts only inline expressions (both simple and compound) and allows to substitute expr
with ...
named argument values.
within
Passing language objects to expr
is generally not intended but can be achieved with do.call
.
Only single expression
s will work and substitution is not available. See examples.
# evaluate code using within
q <- qenv()
q <- within(q, {
i <- iris
})
q <- within(q, {
m <- mtcars
f <- faithful
})
q
get_code(q)
# inject values into code
q <- qenv()
q <- within(q, i <- iris)
within(q, print(dim(subset(i, Species == "virginica"))))
within(q, print(dim(subset(i, Species == species)))) # fails
within(q, print(dim(subset(i, Species == species))), species = "versicolor")
species_external <- "versicolor"
within(q, print(dim(subset(i, Species == species))), species = species_external)
# pass language objects
expr <- expression(i <- iris, m <- mtcars)
within(q, expr) # fails
do.call(within, list(q, expr))
exprlist <- list(expression(i <- iris), expression(m <- mtcars))
within(q, exprlist) # fails
do.call(within, list(q, do.call(c, exprlist)))
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