[R] "tree": Extracting deviance & Gaussian model of the node?

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From: Tak Kaneko (nospam@nospamcam.ac.uk)
Date: Tue 08 May 2001 - 03:04:29 EST 

Message-ID: <Pine.SOL.4.33.0105071803300.10327-100000@green.csi.cam.ac.uk>

Hi

I'm trying to use the "tree" package in R to predict intonation for a
speech synthesiser and when I feed the feature vector into the tree,
I want to get the predicted value and the deviance associated with that
node.

Q.1 

---
I was hoping that the following command will return a tree object of the
predicted values, but I get the following error:

------------------------------------------------------------
> test.tr <- predict.tree(pr,test.data,type="tree")
Error in as.list(X) : Object "response.names" not found

where:
pr = 	A tree was grown using the training data and then pruned back to
	where the deviance was minimised when a separate test data set was
	used. "pr" is this pruned tree.

test.data = test data with the features and response
-------------------------------------------------------------

How would I be able to access the prediction and the deviance? Would this
work if the data was a feature vector with no responses? (as would be the
case when it comes to predicting the real thing).

Q.2
---
Assuming that the distribution of the data at each node is Gaussian, I'd
like to model each node as a gaussian probability density function with a
mean at the predicted value and variance, which is presumably related to
the deviance...

I've found out the definition for the deviance from the S-plus manual but
it's not yet clear to me. So how could I deduce the variance of a value
predicted by "tree"?

Thanks and I'd be grateful if you could also reply to my address above
(nospam@nospamuk).

Tak Kaneko

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