Converting a character string into a data frame name and performing assignments to that data frame

Hi,
I'd greatly appreciate any insight into the problem in my previous
message below: Please note that I would like to loop through the
following steps for a list of data frames whose names are dynamically
assigned at run time, so I have a character string variable, called
"variable.df", which stores the name of the data frame at any given
point ...and I need to be able to manipulate the contents of the data
frame somehow using this character string :

   

colnames(variable.df) = colnames(some.other.df)
variable.df = rbind(variable.df, some.other.df)
write.table(variable.df, file=some.file)
     

Thanks!
Kavitha

On Sat, Mar 20, 2010 at 5:07 PM, Kavitha Venkatesan
<kavitha.venkatesan at gmail.com>  wrote:
   

Hi,

I would like to do the following operations:

variable.df is a character string that contains the name of the data
frame that I want to do the following operations on:

variable.df<- data.frame();
# I can do the above command using
assign( variable.df, data.frame() )

How can I perform the assignment statements below ?

colnames(variable.df) = colnames(some.other.df)
variable.df = rbind(variable.df, some.other.df)
write.table(variable.df, file=some.file)

Doing
eval(  substitute( colnames(var), list(var=as.name(variable.df) ) ) )
  didn't get me all the way there.

Thanks!
Kavitha

     

Hi,
I'm not sure what your goal is, but why don't you use a list?

You can store each new dataframe name in a new element of the list.
At the end, if each element has the same length, you can use as.data.frame() 
or something similar.

my.dfs <- new.env()
dfname <- 'a.df'
assign(dfname, as.data.frame(diag(2)),env=my.dfs)
dfname <- 'b.df'
assign(dfname, as.data.frame(diag(3)),env=my.dfs)
ls(my.dfs)

sapply(my.dfs,function(x) coef(lm(V1~.,x)))

Since you didn't provide any sample data, I'm not sure if that's really what 
you're looking for, but what I said might get you started.
I'm no expert, but I might be able to help you a bit further if you provide 
the necessary information (which you can find in the posting guide)

Ivan

Le 4/7/2010 18:13, Kavitha Venkatesan a ?crit :

 Hi,
 I'd greatly appreciate any insight into the problem in my previous
 message below: Please note that I would like to loop through the
 following steps for a list of data frames whose names are dynamically
 assigned at run time, so I have a character string variable, called
 "variable.df", which stores the name of the data frame at any given
 point ...and I need to be able to manipulate the contents of the data
 frame somehow using this character string :

 colnames(variable.df) = colnames(some.other.df)
 variable.df = rbind(variable.df, some.other.df)
 write.table(variable.df, file=some.file)

 Thanks!
 Kavitha

 On Sat, Mar 20, 2010 at 5:07 PM, Kavitha Venkatesan
 <kavitha.venkatesan at gmail.com>  wrote:

 Hi,

 I would like to do the following operations:

 variable.df is a character string that contains the name of the data
 frame that I want to do the following operations on:

 variable.df<- data.frame();
 # I can do the above command using
 assign( variable.df, data.frame() )

 How can I perform the assignment statements below ?

 colnames(variable.df) = colnames(some.other.df)
 variable.df = rbind(variable.df, some.other.df)
 write.table(variable.df, file=some.file)

 Doing
 eval(  substitute( colnames(var), list(var=as.name(variable.df) ) ) )
   didn't get me all the way there.

 Thanks!
 Kavitha

-- 
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. S?ugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra at uni-hamburg.de

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