[R] data frame names in sequence. please help!!!

[Zoho]

Thank you all. The 'list' works well, except makes a really big 'list', since
my data is 'huge'. But solves the problem anyway. Appreciate a lot! 


Barry Rowlingson wrote:
> 
> On Sun, Jan 10, 2010 at 7:16 AM, Berend Hasselman <bhh at xs4all.nl> wrote:
>>
>>
>>
>> Zoho wrote:
>>>
>>> I've been stuck with this problem for a whole afternoon. It's silly but
>>> totally pissed me off. I have a set of data frames with names in a
>>> sequence: df_1, df_2, df_3, ..., df_20. Now I want to access each data
>>> frame (read or write) in a for loop, in a way something like this:
>>>
>>> for (i in 1:20) {
>>>   df_i <- ######
>>>   length(which(df_i[,7]==1))
>>>   ######
>>> }
>>>
>>> I tried paste or cat ("df_", i, sep=""). But neither way works. Your
>>> help
>>> is highly appreciated!! Thanks in advance!
>>>
>>
>> df_1 <- data.frame(x1=3,x2=5)
>> df_2 <- data.frame(x1=2,x2=7)
>> df_3 <- data.frame(x1=-1,x2=1)
>>
>> for(k in 1:3){v <- paste("df_",k,sep=""); print(get(v))}
>> for(k in 1:3){v <- paste("df",k,sep="_"); print(get(v)[,2])}
>>
>> Have a look at get:
>>
>> ?get
> 
>  Or better still, have a look at making a *list* instead of a bunch of
> data frames with numbers in their names, then you can index in a
> sensible way without having to construct names with paste and get.
> Here's a list of data frames:
> 
>  L = list()
>  for(i in 1 :10){
>   L[[i]]=data.frame(x=runif(10))
> }
> 
>  Now you can loop over L[[i]]
> 
>  This has been asked a zillion times on R-help. Sure, if you've
> already mistakenly created 200 data frames then you need the paste/get
> solution, but don't make the same mistake twice. Use a list.
> 
> Barry
> 
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> 
> 

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