[R] evaluating expressions as R console

[Bert Gunter]

You might want to look at the "evaluate" package.

Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sun, Sep 4, 2016 at 4:47 PM, Adrian Dușa <dusa.adrian at unibuc.ro> wrote:
> Dear R users,
>
> I am trying to simulate a pseudo R console, evaluating commands. This is a
> simple example of a series of command lines which get evaluated:
>
> foo <- function(x) {
>     print(x)
> }
> print)foo)
> foo(2)
>
>
> If I copied and pasted this example in an R console, this is the result to
> replicate (and the benchmark to compare everything else):
>
>> foo <- function(x) {
> +     print(x)
> + }
>> print)foo)
> Error: unexpected ')' in "print)"
>> foo(2)
> [1] 2
>
>
> The trouble I'm having is to reproduce this exact output, by evaluating the
> chunk of code. I tried both Rscript and littler, but I am unable to
> reproduce this.
>
> I had some success via:
>
> R CMD BATCH -q foo.R
>
> (saving the chunk to a file called foo.R), which only works until the first
> error appears. I can run it again on the subsequent command(s) after the
> error, but the function foo(), which in a normal R console gets created
> without any error, doesn't get preserved on the next run.
>
> I also had some limited success with:
>
> source("foo.R", echo = TRUE, keep.source = TRUE)
>
> But the error message is different, and the first 4 lines are not echo-ed.
>
> source() works pretty well if there are no errors, but otherwise I get the
> same result as R CMD BATCH, namely only the error is displayed and the
> function foo() doesn't get created in the current environment.
>
> I would rather use source() than R CMD BATCH, due to specific environments
> where the chunk should be evaluated in (not impossible, but inconvenient to
> save environments and load them back in the R CMD BATCH).
>
> Was also curious about knitr and pander, but again unable to replicate the
> results in the real R console.
>
> After many hours of searching, reading and testing, I would be grateful for
> any hint.
>
> Thank you in advance,
> Adrian
>
> --
> Adrian Dusa
> University of Bucharest
> Romanian Social Data Archive
> Soseaua Panduri nr.90
> 050663 Bucharest sector 5
> Romania
>
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>
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