Re: Batch update of datetime stamp.

["Thomas Jagger" <tjagger@blarg.net>]

Sarah,

Yes by name is needed, try the following:

clean.all <-function(id)
{
obj.name<-paste("station",id,sep="")
value<-clean.dates(get(where=1,obj.name)$weather.date)
eval(substitute(X$weather.date<-VALUE,list(X=as.name(obj.name),VALUE=value))
,local=F)
id
}

Test case:

station4<-data.frame(weather.date=c(1,2,3,4),junk=1:4)
clean.dates<-function(x) x^2

Some notes:

1. You must substitute both X and VALUE, since evaluation is at the top
level.  
2. Using local=F makes the evaluation performed in the top level frame (1).
This is the calling frame. In fact local=T wont work even with "<<-".
3. where=1, use position one. I assume that your data is in the working
directory. 
4. I returned the id, thus if you are running this and it crashes, you could
check the list of ids (provided you save/print them), since changes are made
in the working directory at the time of the eval call.

Tom Jagger
Research Associate
FSU department of Geography
-----Original Message-----
From: s-news-owner@lists.biostat.wustl.edu
[mailto:s-news-owner@lists.biostat.wustl.edu] On Behalf Of Sarah Henderson
Sent: Monday, July 18, 2005 2:42 PM
To: s-news@lists.biostat.wustl.edu
Subject: [S] Batch update of datetime stamp.


Now that Monday has rolled around I am trying to combine all the victories 
of last week.

I have successfully imported my 300+ .xls files into S-Plus data frames, 
all of which have names of the form 'stationID' where ID is any number 
between 60 and 800.  All data frames have the column 'weather.date'

I have successfully written a 'clean.dates' function that will clean the 
'weather.date' column of any data frame with the following expression:
stationID$weather.date <- clean.dates(stationID$weather.date)

What I would like to do now is write another function that cleans the 
'weather.date' columns for all 300+ data frames, but I cannot see a way to 
coerce the data frame names out of the function's parameter.


If I try:

clean.all <- function(id){
         frame.name <- paste("station", id, sep="")
         as.name(frame.name)$weather.date <- 
clean.dates(as.name(frame.name)$weather.date)}

I get the error message: Problem in .A0$weather.date <- .A1: Meaningless to 
append to mode "name"


If I try:

clean.all <- function(id){
                 eval(as.name(paste("station", id, sep="")))$weather.date <-
                         clean.dates(eval(as.name(paste("station", id, 
sep="")))$weather.date)}

I get the error message: Problem in all.dates: Invalid nested assignment: 
mode "character", expected name: eval(as.name(paste("station",        67, 
sep = "")))$weather.date <- clean.dates(
         eval(as.name(paste("station", id, sep = "")))$weather.date)


Unfortunately I have a limited number of tricks up my sleeve and I've run 
out.  I feel as though there should be a simple way to do this but, once 
again, I need further guidance.  A little help would go a long way.

Many thanks (again!),

Sarah

______________________________________________

Sarah Henderson
Department of Health Care & Epidemiology
University of British Columbia
Phone: 604.822.1274
Fax: 604.822.9588

Michael Smith Foundation for Health Research Trainee
Canadian Institutes of Health Research Trainee 

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