[R] Regression Tree Questions

Bert Gunter bgunter.4567 at gmail.com
Sat Feb 24 20:33:43 CET 2018

```But note that converting it e.g. via as.numeric() would be disastrous:

> as.numeric(factor(c(3,5,7)))
[1] 1 2 3

The OP may need to do some homework with R tutorials to learn about basic R
data structures; or if he has already done this, he may need to be more
explicit about how the data were created/entered.

-- Bert

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sat, Feb 24, 2018 at 11:21 AM, José María Mateos <chema at rinzewind.org>
wrote:

> On Sat, Feb 24, 2018 at 01:16:27PM -0600, Gary Black wrote:
> > Hi All,
> >
> > I'm a newbie and have two questions.  Please pardon me if they are very
> basic.
> >
> >
> > 1.  I'm using a regression tree to predict the selling prices of 10 new
> records (homes).  The following code is resulting in an error message:
> pred <- predict(model, newdata = outOfSample[, -6])
> >
> > The error message is:
> >
> > Error in model.frame.default(Terms, newdata, na.action = na.action, xlev
> = attr(object,  :
> > factor Sq. Feet has new levels 1375, 1421, 1547, 1621, 1868, 2211, 2265,
> 2530, 2672, 3365
> >
>
> Seems to me that variable 'Sq. Feet' is being encoded as a factor
> instead of having numerical values. When you train, the model sees a
> series of values that understands as categorical, and when you try to
> predict it is encountering some different categories and it doesn't know
> what to do with them.
>
> As that variable is most probably numeric, it should be read as such.
> You can try converting it on both your train and test datasets.
>
> Cheers,
>
> JMM.
>
> -- José María Mateos
> https://rinzewind.org/blog-es || https://rinzewind.org/blog-en
>
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>

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