R help - Oct 2007 - the difference between temp and .temp

Hi everyone -

This came up within the last day -- Jim's response to Deepankar is pasted
below.

There are probably lots of reasons, but what is the advantage to using
.temp over, say, temp?

I often find myself writing temporary objects -- should I use the .
preface?  What would be the advantages to doing so?

Thanks in advance for what will surely be a collection of illuminating
responses.

tim




On 10/25/07, jim holtman <jholtman at gmail.com>
wrote:
> Actually I forgot you have a data frame. so use:
>
> for (i in 1:18){
>     .temp <- yourDataFrame[[paste('b', i, sep='')]]
>     ....   use .temp ....
> }
>
>
> On 10/24/07, DEEPANKAR BASU <basu.15 at osu.edu> wrote:
> > Hi All,
> >
> > I have a data frame with a group of variables named b1, b2, b3, ...,
b18. These variables take the value 1, 2 or NA. For each observation, I want to
do some computation by looping over the values for the group of variables: b1 to
b18. In STATA I would do:
> >
> > forval i=1/18 {
> >  --- use b`i' for computation ----
> > }
> >
> > How can this be done in R?
> >
> > Deepankar
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > 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.
> >
>
>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem you are trying to solve?
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>



-- 
Tim Calkins
0406 753 997

On 26/10/2007, at 11:44 AM, Tim Calkins wrote:
> Hi everyone -
>
> This came up within the last day -- Jim's response to Deepankar is  
> pasted below.
	(but snipped out of this response).
> There are probably lots of reasons, but what is the advantage to using
> .temp over, say, temp?
>
> I often find myself writing temporary objects -- should I use the .
> preface?  What would be the advantages to doing so?
>
> Thanks in advance for what will surely be a collection of illuminating
> responses.
The difference is that you see ``temp'' when you do an ls() of your
workspace, and you don't see ``.temp'' --- it's hidden.  Unless
you ask
particularly nicely!

The advantage of using .temp is that you can't see it (so it doesn't  
clutter things up).

The ***dis**advantage of using .temp is that you can't see it! :-)

I guess the rationale for using .temp is the presumption that if you  
can't see it
you don't really want it.  I.e. overwriting something called .temp is  
unlikely to lose
you an object that you desperately wanted to keep.  If you were  
passionately fond
of the contents of .temp, you would've named the object in such a way  
that you
could look at it from time to time without having to make a special  
effort (having to set
all.names=TRUE).

OTOH something called temp is unlikely to be something of which you are
passionately fond anyhow.

			cheers,

				Rolf Turner

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On 25/10/2007 7:11 PM, Rolf Turner wrote:
> 
> OTOH something called temp is unlikely to be something of which you are
> passionately fond anyhow.
Unless you put your thousand year temperature records into it.

Duncan Murdoch