R help - Jan 2021 - Why is rm(list=ls()) bad practice?

rm(list=ls()) is a bad practice... especially when posting examples. It
doesn't clean out everything and it removes objects created by the user.

Read ?data.frame, particularly regarding the check.names parameter. The intent
is to make it easier to use DF$A notation, though DF$`(A)` is usable if you are
somewhat experienced with R.

On January 21, 2021 12:58:44 PM PST, Bernard McGarvey <mcgarvey.bernard at
comcast.net> wrote:
>Here is an example piece of code to illustrate an issue:
>
>rm(list=ls()) # Clear Workspace
>#
>Data1 <- matrix(data=rnorm(9,0,1),nrow=3,ncol=3)
>Colnames1 <- c("(A)","(B)","(C)")
>colnames(Data1) <- Colnames1
>print(Data1)
>DataFrame1 <- data.frame(Data1)
>print(DataFrame1)
>colnames(DataFrame1) <- Colnames1
>print(DataFrame1)
>
>The results I get are:
>
>            (A)        (B)        (C)
>[1,]  0.4739417  1.3138868  0.4262165
>[2,] -2.1288083  1.0333770  1.1543404
>[3,] -0.3401786 -0.7023236 -0.2336880
>        X.A.       X.B.       X.C.
>1  0.4739417  1.3138868  0.4262165
>2 -2.1288083  1.0333770  1.1543404
>3 -0.3401786 -0.7023236 -0.2336880
>         (A)        (B)        (C)
>1  0.4739417  1.3138868  0.4262165
>2 -2.1288083  1.0333770  1.1543404
>3 -0.3401786 -0.7023236 -0.2336880
>
>so that when I make the matrix with headings the parentheses are
>replaced by periods but I can add them after creating the data frame
>and the column headings are correct. 
>
>Any ideas on why this occurs?
>
>Thanks
>
>
>Bernard McGarvey
>Director, Fort Myers Beach Lions Foundation, Inc.
>Retired (Lilly Engineering Fellow).
>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
-- 
Sent from my phone. Please excuse my brevity.

In a separate thread Jeff Newmiller wrote:
> rm(list=ls()) is a bad practice... especially when posting examples. It
doesn't clean out everything and it removes objects created by the user.
This query is to ask

1) Why is it bad practice to clear the workspace when presenting an example?
I'm assuming here that people who will try R-help examples will not run them
in the
middle of something else, which I agree would be unfortunates. However, one of
the
not very nice aspects of R is that it is VERY easy to have stuff hanging around
(including
overloaded functions and operators) that get you into trouble, and indeed make
it harder
to reproduce those important "minimal reproducible examples".  This
includes the .RData
contents. (For information, I can understand the attraction, but I seem to have
been
burned much more often than I've benefited from a pre-warmed oven.)

2) Is there a good command that really does leave a blank workspace? For testing
purposes, it would be useful to have an assured blank canvas.

This post is definitely not to start an argument, but to try to find ways to
reduce
the possibilities for unanticipated outcomes in examples.

Cheers, JN