R help - Sep 2011 - How make a x,y dataset from a formula based entry

Hello all, 

So I am using the (formula entry) method for randomForests:

randomForest(y~x1+x2+...+x39+x40,data=xxx,...) but the issue is that some of
the items in that package dont take a formula entry - you have to explicitly
state the y and x vector:

randomForest(x=xxx[,c('x1','x2',...,'x40')],y=xxx[,'y'],...)

Now my question is whether there is a function/way to tell R to take a
formula and make the two corresponding datasets [x,y] (that way I dont have
to create the x dataset manually with all 40 variables I have).

There must be a more elegant way to do this than
x=xxx[,c('x1','x2',...,'x40')] 

Thanks!
George

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Hello,
You can check ?model.frame.
I do not know however to extract only the right-hand of left-hand part
of a formula.

JC

2011/9/22 trekvana <trekvana at aol.com>:
> Hello all,
>
> So I am using the (formula entry) method for randomForests:
>
> randomForest(y~x1+x2+...+x39+x40,data=xxx,...) but the issue is that some
of
> the items in that package dont take a formula entry - you have to
explicitly
> state the y and x vector:
>
>
randomForest(x=xxx[,c('x1','x2',...,'x40')],y=xxx[,'y'],...)
>
> Now my question is whether there is a function/way to tell R to take a
> formula and make the two corresponding datasets [x,y] (that way I dont have
> to create the x dataset manually with all 40 variables I have).
>
> There must be a more elegant way to do this than
> x=xxx[,c('x1','x2',...,'x40')]
>
> Thanks!
> George
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/How-make-a-x-y-dataset-from-a-formula-based-entry-tp3834477p3834477.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

To separate the parts of a formula, use as.character
(check the examples in ?character)

Helios

22 Sep 2011 16:14:05 -0400
From: Jean-Christophe BOU?TT? <jcbouette at
gmail.com>
> Hello,
> You can check ?model.frame.
> I do not know however to extract only the right-hand of left-hand
part
> of a formula.
> 
> JC
> 
> 2011/9/22 trekvana <trekvana at aol.com>:
>> Hello all,
>>
>> So I am using the (formula entry) method for randomForests:
>>
>> randomForest(y~x1+x2+...+x39+x40,data=xxx,...) but the issue is that
some of
>> the items in that package dont take a formula entry - you have to
explicitly
>> state the y and x vector:
>>
>>
randomForest(x=xxx[,c('x1','x2',...,'x40')],y=xxx[,'y'],...)
>>
>> Now my question is whether there is a function/way to tell R to take
a
>> formula and make the two corresponding datasets [x,y] (that way I
dont have
>> to create the x dataset manually with all 40 variables I have).
>>
>> There must be a more elegant way to do this than
>> x=xxx[,c('x1','x2',...,'x40')]
>>
>> Thanks!
>> George

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On Thu, Sep 22, 2011 at 2:54 PM, trekvana <trekvana at aol.com>
wrote:
> Hello all,
>
> So I am using the (formula entry) method for randomForests:
>
> randomForest(y~x1+x2+...+x39+x40,data=xxx,...) but the issue is that some
of
> the items in that package dont take a formula entry - you have to
explicitly
> state the y and x vector:
>
>
randomForest(x=xxx[,c('x1','x2',...,'x40')],y=xxx[,'y'],...)
>
> Now my question is whether there is a function/way to tell R to take a
> formula and make the two corresponding datasets [x,y] (that way I dont have
> to create the x dataset manually with all 40 variables I have).
>
> There must be a more elegant way to do this than
> x=xxx[,c('x1','x2',...,'x40')]
We assume that the formula is of the form:

fo <- y ~ x1 + x2 + x3

Now if we set:

v <- all.vars(fo)

and if DF is our data frame then DF[, v[1]] and DF[v[-1]] are the
response and predictors.  (You may need to add an intercept to the
predictors and convert the predictors from data frame to a matrix
depending on what you intend to do next.)

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