withCapture: Evaluates an expression and captures the code and/or the...

In R.utils: Various Programming Utilities

Evaluates an expression and captures the code and/or the output

Description

Evaluates an expression and captures the code and/or the output.

Usage

withCapture(expr, replace=getOption("withCapture/substitute", ".x."), code=TRUE,
  output=code, ..., max.deparse.length=getOption("max.deparse.length", 10000), trim=TRUE,
  newline=getOption("withCapture/newline", TRUE), collapse="\n", envir=parent.frame())

Arguments

expr	The R expression to be evaluated.
replace	An optional named list used for substituting symbols with other strings.
code	If TRUE, the deparsed code of the expression is echoed.
output	If TRUE, the output of each evaluated subexpression is echoed.
...	Additional arguments passed to sourceTo which in turn passes arguments to source().
max.deparse.length	A positive integer specifying the maximum length of a deparsed expression, before truncating it.
trim	If TRUE, the captured rows are trimmed.
newline	If TRUE and collapse is non-NULL, a newline is appended at the end.
collapse	A character string used for collapsing the captured rows. If NULL, the rows are not collapsed.
envir	The environment in which the expression is evaluated.

Value

Returns a character string class 'CapturedEvaluation'.

Author(s)

Henrik Bengtsson

See Also

Internally, eval() is used to evaluate the expression.

Examples

print(withCapture({
 n <- 3
 n

 for (kk in 1:3) {
   printf("Iteration #%d\n", kk)
 }

 print(Sys.time())

 type <- "horse"
 type
}))

## > n <- 3
## > n
## [1] 3
## > for (kk in 1:3) {
## +     printf("Iteration #%d\n", kk)
## + }
## Iteration #1
## Iteration #2
## Iteration #3
## > print(Sys.time())
## [1] "2011-11-06 11:06:32 PST"
## > type <- "horse"
## > type
## [1] "horse"


# Automatic "variable" substitute
# (disable with relabel=NULL)
a <- 2
b <- "Hello world!"

print(withCapture({
 x <- .a.
 s <- .b.
 x
 s
}))

## > x <- 2
## > s <- "Hello world!"
## > x
## [1] 2
## > s
## [1] "Hello world!"

R.utils documentation built on Nov. 18, 2023, 1:09 a.m.