[R] Data.frames : difference between x$a and x[, "a"] ? - How set new values on x$a with a as variable ?

[Ista Zahn]

On Fri, Sep 10, 2010 at 9:22 AM, omerle <omerle at laposte.net> wrote:
>> Message du 10/09/10 14:53
>> De : "Ista Zahn"
>> A : "omerle"
>> Copie à : r-help at r-project.org
>> Objet : Re: [R] Data.frames : difference between x$a and x[, "a"] ? - How set new values on x$a with a as variable ?
>>
>>
>> Hi,
>>
>> On Fri, Sep 10, 2010 at 4:05 AM, omerle wrote:
>> > Hi,
>> >
>> > I got two questions :
>> >
>> > 1st Question
>> >             a="S"
>> >             b=data.frame(S=3)
>> >             do.call(`<-`,list(do.call(`$`,list(b,"S")),5))
>>
>> I think there is some confusion here. Why are you setting a equal to
>> "S" but then never using it?
>>
>> > => How can I put new values on S column having the column name as a variable ?
>>
>> I'm having trouble parsing this. What exactly do you want to do?
> 1 - Put a list as an element of a data.frame. That's quite convenient for my pricing function.

I think this is a really bad idea. data.frames are not meant to be
used in this way. Why not use a list of lists?

>
>> >
>> > 2 nd Question
>> >        a="S"
>> >        b=data.frame(S=3)
>> >        b[,"S"]=list(1:10) #Doesnt works
>> >        b$S=list(1:10) #Works
>> > => Isnt the same thing ? What is the difference between these two things ?
>>
>> I believe b[["S"]] is the same as b$S, b[,"S"] is different. But I
>> have to question your assertion that b$S=list(1:10) "Works". This is a
>> very odd construction (putting a list as an element of a data.frame)
>> and is almost certainly not what you want.
> 2 - That's what I want. I figured out just five minutes ago that b[["S"]] works because it's the same thing as b$S.
> But I still dont know what is b[,"S"] compared to b[["S"]]

see ?"["

>> >
>> >
>> > Thanks,
>> >
>> > Une messagerie gratuite, garantie à vie et des services en plus, ça vous tente ?
>> > Je crée ma boîte mail www.laposte.net
>> >
>> >        [[alternative HTML version deleted]]
>> >
>> >
>> > ______________________________________________
>> > R-help at r-project.org mailing list
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>> >
>> >
>>
>>
>>
>> --
>> Ista Zahn
>> Graduate student
>> University of Rochester
>> Department of Clinical and Social Psychology
>> http://yourpsyche.org
>>
>>
>
> Une messagerie gratuite, garantie à vie et des services en plus, ça vous tente ?
> Je crée ma boîte mail www.laposte.net
>
>        [[alternative HTML version deleted]]
>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>



-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org