R help - Jul 2009 - spreadsheet-style autoupdating

Dear all,
I am curious whether one can automatically update, say, a column in R,
similar to how spreadsheets (Excel, etc.) do?
In my specific case I have two columns with logical data, which
individually convey different information, although ultimately for a
common purpose (flagging for removal). I would thus need a third
logical variable that would take TRUE if any of the prev. columns take
value TRUE for the given line. Without using RExcel, would there be a
way of automatising this (by "manual" I understand running some code
to recreate the third variable prior to printing it)?

To R purists: I am not sure that this would amount to good programming
habits. Also, this way of thinking comes from my infancy with Excel;
should there be a better approach, please let me know.
Thank you
Liviu

Hello Patrick,

On 7/15/09, Patrick Burns <pburns at pburns.seanet.com>
wrote:
> How about something along the lines of:
>  apply(twocolumns, 1, any)
>
This efficiently solves the first part of my question. I will probably
content myself with issuing this command each time I update one of the
"twocolumns"; I'm still curious whether R can store this function
in
the third column, and autoupdate it whenever one of the "twocolumns"
gets modified (behaviour very similar to that of spreadsheets),
although I'd doubt R could.

Thank you
Liviu

Hello Steve,

On Thu, Jul 16, 2009 at 2:28 AM, S Ellison<S.Ellison at lgc.co.uk>
wrote:
> Auto-updating sounds hard in R for a 'regular' data frame. You
could
> perhaps define an entirely new class of object and define data
> entry/indexing methods so that, say, they sought functions in an
> attribute defined as a list of lists of the form (target, source, fun)
> and inserted the result of applying function fun to column name(s)
> source into a column named target. But I've not tried it, and you'd
have
> to work out how to append, update and delete the functions as well as
> work out all the possible entry/indexing operators in order to make sure
> you caught all the possibilities for messing up. Sounds nasty.
>
Nasty indeed.

> Much simpler to write your row drop as something simple like
> y.clean<-subset(y, y$bad|y$worse)
> where $bad and $worse are your two 'drop me' flag columns.
>
An(other) efficient solution to the second part of the problem. Now
for this specific case of flagging for removal I no longer need a
third logical, and autoupdating; I can use all relevant variables in
one call. I settled for the following syntax:
> dim(tmp.obj)   #original object
[1] 35771    28
> dim(subset(tmp.obj, !tmp.obj$dupl.yr & !tmp.obj$unmat.yr))   #object
subsetted using the twocols
[1] 35737    28
> dim(subset(tmp.obj, !tmp.obj$rm.yr))   #object subsetted using the third
logical
[1] 35737    28

I needed to replace "|" with "&" to get this result.
I'm also negating
the logicals, since I have TRUE for "remove".
Thank you
Liviu