[R] predict newdata question

[Felipe Carrillo]

 Thanks Bill, that worked great!!
 
> You ask:

# How can I use 
> predict here, 'newdata' 
> 
> crashes
predict(m1,newdata=wolf$predicted);wolf # it doesn't work

To 
> 
> use predict() you need to give a fitted model object (here m1) and a 
> *data 
> frame* to specify the values of the predictors for which you want 
> 
> predictions.  Here wolf$predicted is not a data frame, it is a 
> 
> vector.

What I think you want is

pv <- predict(m1, newdata = 
> 
> wolf)

That will get you linear predictors.  To get probabilities 
> you 
> need to say so as

probs <- predict(m1, newdata = wolf, 
> type = 
> "response")

You can put these back into the data frame if 
> you wish, 
> e.g.

wolf <- within(wold, {
    lpreds <- 
> 
> predict(m1, wolf)
    probs <- predict(m1, wolf, type = 
> 
> "response")
})

Now if you look at 

head(wolf)

you will 
> 
> see two extra columns.


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> 
> Behalf Of Felipe Carrillo
Sent: Saturday, 26 June 2010 10:35 
> AM
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> 
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Subject: 
> 
> [R] predict newdata question

Hi:
I am using a subset of the 
> below 
> dataset to predict PRED_SUIT for
the whole dataset but I am 
> having trouble 
> with 'newdata'. The model
was created with 153 
> records and want to predict 
> for 208 records. 

[lots of stuff 
> 
> 
> omitted]

wolf$prob99<-(exp(wolf$predicted))/(1+exp(wolf$predicted))
head(wolf);dim(wolf)
   
> 
> # How can I use predict here, 'newdata' 
> 
> crashes
 predict(m1,newdata=wolf$predicted);wolf  # it doesn't 
> 
> work

Thanks for any hints


Felipe D. Carrillo
Supervisory 
> 
> Fishery Biologist
Department of the Interior
US Fish & 
> Wildlife 
> Service
California, 
> 
> USA




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