[R] ls() pattern question

[Kai Yang]

 Thanks Andrew. it works well. --- Kai
    On Wednesday, July 14, 2021, 05:22:01 PM PDT, Bert Gunter <bgunter.4567 using gmail.com> wrote:  
 
 Actually fun( param != something..) is syntactically incorrect in the first place for any function! 

ls sees "pat != whatever"  as the "name" argument of ls() and can't make any sense of it, of course. 
 
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 Wed, Jul 14, 2021 at 5:01 PM Andrew Simmons <akwsimmo using gmail.com> wrote:

Hello,


First, `ls` does not support `!=` for pattern, but it's actually throwing a
different error. For `rm`, the objects provided into `...` are substituted
(not evaluated), so you should really do something like

rm(list = ls(pattern = ...))

As for all except "con", "DB2", and "ora", I would try something like

setdiff(ls(), c("con", "DB2", "ora"))

and then add `rm` to that like

rm(list = setdiff(ls(), c("con", "DB2", "ora")))

On Wed, Jul 14, 2021 at 7:41 PM Kai Yang via R-help <r-help using r-project.org>
wrote:

> Hello List,
> I have many data frames in environment.  I need to keep 3 data frames
> only, con DB2 and ora.
> I write the script to do this.
> rm(ls(pattern != c("(con|DB2|ora)")))
>
>
> but it give me an error message:
>
>
> Error in rm(ls(pattern != c("(con|DB2|ora)"))) :
>   ... must contain names or character strings
>
> I think the pattern option doesn't support != ? and is it possible to fix
> this?
> Thank you,
> Kai
>
>
>
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