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R.utils (version 2.0.0)

withCapture: 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, substitute=getOption("withCapture/substitute", ".x."), code=TRUE,
  output=code, ..., max.deparse.length=getOption("max.deparse.length", 10000), trim=TRUE,
  newline=getOption("withCapture/newline", TRUE), collapse="", envir=parent.frame())
expr{The R expression to be evaluated.}
  substitute{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.}
Returns a character string class 'CapturedEvaluation'.
print(withCapture({
 n <- 3;
 n;
 for (kk in 1:3) {
   printf("Iteration #%d", kk);
 print(Sys.time());
 type <- "horse";
 type;
}))
## > n <- 3
## > n
## [1] 3
## > for (kk in 1:3) {
## +     printf("Iteration #%d", 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 substitute=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!"
}
[object Object]
Internally, eval() is used to evaluate the expression.

utilities

Arguments