[R] Conditionally skip over "for(..){" and "}"??

[(Ted Harding)]

Following up on Barry's suggestion led on to a more straightforward
approach:

  VarNames <- NULL
# VarNames <- c(VarNames, "Var1")
# VarNames <- c(VarNames, "Var2")
# VarNames <- c(VarNames, "Var3")
# [...]
  for(i in (1:length(VarNames))){
    VarName <- VarNames[i]
    [...]

Then any one or some of those lines can be uncommented.

With thanks for the suggestions.
Ted.

On 12-Oct-08 11:32:31, Barry Rowlingson wrote:
> 2008/10/12 Ted Harding <Ted.Harding at manchester.ac.uk>:
>> Hi Folks,
>> I'm wondering if there's a secret trick to achieve the following.
>>
>> I have some big code for analysis related to a named variable,
>> which will be one of several in the columns of a dataframe, and
>> I would like to be able to choose between a run for just one of
>> these variables, or a run which loops over them all.
>>
>> So, for a single run, I could have the following kind of thing
>> in a file code.R to be sourced by source("code.R"):
>>
>> # VarName <- "Var1"
>>  VarName <- "Var2"
>> # VarName <- "Var3"
>> # VarName <- "Var4"
>>
>> ### CUT OUT LOOP
>> # VarNames <- c("Var1","Var2","Var3","Var4")
>> # for( VarName in VarNames ) {
>>
>> << Lots of code related to analysis of variable VarName >>
>>
>> ### CUT OUT END OF LOOP
>> # }
>>
>> which would do the single case for Var2. A run for a different VarName
>> would be done by editing the first block to select the new VarName.
>>
>> Now, when I want to run the loop over all VarNames, I could of course
>> likewise edit the file so as to uncomment the code which follows the
>> "CUT OUT ..." lines. But I would prefer to avoid having to do the
>> latter, and am therefore wondering if there is some way to
>> conditionally
>> skip over those bits of code.
> 
>  What's the problem with doing a loop over a single VarName in
> VarNames? I'd put something like:
> 
>  VarNames = c(
> "Var1",
> "Var2",
> "Var3"
> )
> 
>  at the start of my code for easy editing, and then if I only wanted
> to do it for one VarName you can just do:
> 
> VarNames = c(
>#"Var1",
> "Var2"
>#"Var3"
> )
> 
>  - it's just a shame that R doesn't like trailing commas in c() calls,
> which would make it even easier.
> 
>  Of course the real way to do it is to rewrite it as a function and do
> foo(c("Var1","Var2")) as desired....
> 
> Barry
> 
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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 12-Oct-08                                       Time: 16:00:14
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