R help - Dec 2007 - modify a data.frame within a function

Hello all,
I'm trying to modify a single column of a data frame to remove randomly half
of the values. I want to do it within a function, but can not assign the
modified column back into the data frame. It was easy and successful without a
function, so I suspect the problem is the call of the single column within the
function.

removedata<-function(datafull,var.removed)
{
attach(datafull)
NArandom<-rnorm(n=length(var.removed), mean=0, sd=1)
for (i in 1:length(var.removed))
  if(NArandom[i]>0) 
    var.removed[i]<-"NA" 
datamiss<<-datafull
detach(datafull)
}

-- Yuval Sapir, PhDResearcherInstitute of Evolution, Haifa UniversityHaifa,
Israel 3190‎

	[[alternative HTML version deleted]]

You need to read about scope.

Try using return() from within your function to return the modified
data frame to the caller.

Best wishes,

Mark

On 15/12/2007, Yuval Sapir <ysapir at bgu.ac.il>
wrote:
>  Hello all,
> I'm trying to modify a single column of a data frame to remove randomly
half of the values. I want to do it within a function, but can not assign the
modified column back into the data frame. It was easy and successful without a
function, so I suspect the problem is the call of the single column within the
function.
>
> removedata<-function(datafull,var.removed)
> {
> attach(datafull)
> NArandom<-rnorm(n=length(var.removed), mean=0, sd=1)
> for (i in 1:length(var.removed))
>   if(NArandom[i]>0)
>     var.removed[i]<-"NA"
> datamiss<<-datafull
> detach(datafull)
> }
>
> -- Yuval Sapir, PhDResearcherInstitute of Evolution, Haifa UniversityHaifa,
Israel 3190?
>
>         [[alternative HTML version deleted]]
>
>
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-- 
Dr. Mark Wardle
Specialist registrar, Neurology
Cardiff, UK