[R] small problem with predict

[Petr Pikal]

Hi Ann

As I read your code mode closely, I suspect that there could be 
another variables x1 and x2 somewhere in your search path which 
led to the error.

With fresh R session without any data this works as expected

dold<-data.frame(x1=rnorm(10),x2=5*rnorm(10))
y<-1:10
predict(lm(y~x1+x2,dold),dn,se.fit=T)

Cheers 
Petr

On 16 Jul 2004 at 13:19, Petr Pikal wrote:

> Hi
> 
> On 16 Jul 2004 at 12:38, Anne wrote:
> 
> > hello to all!
> > 
> > I have a small problem wit predict() for lm
> > 
> > Let's say I have predictors x1 and x2, response y
> > 
> > I want to predict for a new ds say
> > dn<-data.frame(x1=
> > seq(min(x1),max(x1),length=10),x2=rep(median(x2),10))
> > 
> > predict(lm(y~x1+x2),dn,se.fit=T)
> > 
> > 
> > Error message
> > >  Error: variables 'x1', 'x2' were specified differently from the
> > >  fit
> 
> AFAIK predixt require to be fed by dataframe in which the 
> variables has the same names as was in lm() call. Either call lm()
> with variables named "x1" and "x2" or build the dataframe "dn" with
> names identical as are names in lm() call
> 
> Cheers
> Petr
> 
> 
> > 
> > (I looked in the help and found the example
> > 
> >  x <- rnorm(15)
> >      y <- x + rnorm(15)
> >     new <- data.frame(x = seq(-3, 3, 0.5))
> >      predict(lm(y ~ x), new, se.fit = TRUE)
> > 
> > where is the difference?)
> > 
> > 
> > Anne
> > 
> > ----------------------------------------------------
> > Anne Piotet
> > Tel: +41 79 359 83 32 (mobile)
> > Email: anne.piotet at m-td.com
> > ---------------------------------------------------
> > M-TD Modelling and Technology Development
> > PSE-C
> > CH-1015 Lausanne
> > Switzerland
> > Tel: +41 21 693 83 98
> > Fax: +41 21 646 41 33
> > --------------------------------------------------
> > 
> >  [[alternative HTML version deleted]]
> > 
> > ______________________________________________
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> 
> Petr Pikal
> petr.pikal at precheza.cz
> 
> ______________________________________________
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Petr Pikal
petr.pikal at precheza.cz