[R] Problem with sample session

[Stephen Meskin]

Thanks Greg for your response. Is there a work around?

Of course this begs the question as to Why is attach part of the sample session in App. A of the introductory manual? All the commands are directly from App. A. Is it possible the configuration of R on my computer is not in accord with acceptable practice? I.e. Could my configuration be set so that attach works as App. A intends?
If not then App. A needs to be changed to replace attach.
If so, then App. A needs to provide instructing on appropriate configuration of R for newbies.

Stephen Meskin
Sent from my iPad

> On May 29, 2014, at 1:06 PM, Greg Snow <538280 at gmail.com> wrote:
> 
> This is a warning and in your case would not be a problem, but it is
> good to think about and the reason why it is suggested that you avoid
> using attach and be very careful when you do use attach.  What is
> happening is that you first created a vector named 'x' in your global
> workspace, you then create a data frame that contains a column that is
> a copy of 'x' that is also named 'x' and the data frame also has
> another column named 'y'.  You then later attach the data frame to the
> search list (if you run the 'search()' command you will see your
> search list).  This is convenient in that you can now access 'y' by
> typing its name instead of something like 'dummy$y', but what happens
> if you just type x?  The issue is that there are 2 objects on your
> search path with that same name.  For your example it will not matter
> much because they have the same value, but what if you run a command
> like 'x <- 3', now you will see a single value instead of a vector of
> length 20 which can lead to hard to find errors.  This is why R tries
> to be helpful by warning you that there are multiple objects named 'x'
> and therefore you may not be accessing the one that you think.  If you
> use attach without being careful it is possible to plot (or regress or
> ...) one variable from one dataset against another variable from a
> completely unrelated dataset and end up with meaningless results.  So,
> if you use attach, be careful.  You may also want to look at the
> followng functions for help with dealing with these issues: conflicts,
> find, get, with, within
> 
>> On Wed, May 28, 2014 at 11:55 PM, Stephen Meskin <actuary at umbc.edu> wrote:
>> While following the suggestion in the manual "An Introduction to R" to
>> begin with Appendix A, I ran into the problem shown below about 3/4 of
>> the way down the 1st page of App. A.
>> 
>> After using the function /attach/, I did not get visible columns in the
>> data frame as indicated but the rather puzzling message emphasized below.
>> 
>> I am running R version 3.1.0 (2014-04-10) using Windows XP.  Thanks in
>> advance for your help.
>> 
>>>> x<-1:20
>>>> w<-1+sqrt(x)/2
>>>> dummy<-data.frame(x=x, y=x+rnorm(x)*w)
>>>> dummy
>>>    x         y
>>> 1   1  2.885347
>>> ...
>>>> fm<- lm(y ~ x, data=dummy)
>>>> summary(fm)
>>> 
>>> Call:
>>> ...
>>>> fm1<- lm(y ~ x, data=dummy,weight=1/w^2)
>>>> summary(fm1)
>>> 
>>> Call:
>>> ...
>>>> attach(dummy)
>>> *_The following object is masked _by_ .GlobalEnv:
>>> 
>>>    x_**_
>>> _*
>> 
>> --
>> /Stephen A Meskin/, PhD, FSA, MAAA
>> Adjunct Assistant Professor of Mathematics, UMBC
>> 
>> **//
>> 
>>        [[alternative HTML version deleted]]
>> 
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> 
> 
> 
> -- 
> Gregory (Greg) L. Snow Ph.D.
> 538280 at gmail.com
>