[R] referencing a data frame with a pointer, link, alias, etc

[Jim Lemon]

On Thu, 29 May 2014 01:13:10 PM dansawyer wrote:
> Good afternoon.
> 
> The question is: does R support pointer like structures? The specific
> problem is:
> 
> a function supporting operations on a set of data frames with similar
> structures.
> 
> I have a set of data frames with similar structures. I wish to perform
> similar operations on those data frames. I have successfully created 
and
> tested the operations and am ready to write a local function to 
perform
> them. To clarify the question below is a pigeon example for the 
question:
> 
> df1 <- (col1, col2, ...)
> df2 <- (col1, col2, ...)
> 
> function f(var)
> {var$col1 <- ...
> var$col2 <- ...
> }
> 
> f(df1)
> 
> Each of the data frames have common column names
> 
> I would like for f to be able to perform operations on the data frames 
from
> within the function. I have tried testing variables without success. R
> allows for creating the necessary 'strings' with the correct names, 
however
> I am unable to bind, transform those strings to reference the data 
frames.
> 
> 
Hi dansawyer,
I may not completely understand what you want to do, but I think you 
want the "get" function to sequentially process your dataframes. 
Maybe something like this:

for(df in paste("df",1:10,sep="")) {
 var<-get(df)
 #do your processing on "var"
}

If you want to read in say, CSV files one at a time:

for(df in paste("df",1:10,".csv",sep="")) {
 var<-read.csv(df)
 #do your processing on "var"
}

You may also want to define a class that specifies the structure of your 
dataframes.

Jim