[R] External validation for a hurdle model (pscl)

[Bert Gunter]

This list is (mostly) about R programming. Your query is (mostly) about
statistics. So you should post on a statistics site like
stats.stackexchange.com
not here; I am pretty sure you'll receive lots of answers there.

Cheers,
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 Tue, Jan 8, 2019 at 10:18 AM Maria Eugenia Utgés <mariaeugeniau using gmail.com>
wrote:

> Hi R-list,
> We have constructed a hurdle model some time ago.
> Now we were able to gather new data in the same city (38 new sites), and
> want to do an external validation to see if the model still performs ok.
> All the books and lectures I have read say its the best validation option
> but...
> I have made a (simple) search, but it seems that as having new data for a
> model is rare, have not found anything with the depth enough so as to
> reproduce it/adapt it to hurdle models.
>
> I have predicted the probability for non-zero counts
> nonzero <- 1 - predict(final, newdata = datosnuevos, type = "prob")[, 1]
>
> and the predicted mean from the count component
> countmean <- predict(final, newdata = datosnuevos, type = "count")
>
> I understand that "newdata" is taking into account the new values for the
> independent variables (environmental variables), is it?
>
> So, I have to compare the predicted values of y (calculated with the new
> values of the environmental variables) with the new observed values.
>
> That would be using the model (constructed with the old values), having as
> input the new variables, and having as output a "new" prediction, to be
> contrasted with the "new" observed y.
>
> These comparison would be by means of AUC, correct classification, and/or
> what other options? Results of the external validation would just be a % of
> correct predicted values? plots?
>
> Need some guidance, sorry if the explanation was "basic" but needed to
> write it in my own words so as not to miss any detail.
>
> Thank you very much in advance,
>
> María Eugenia Utgés
>
> CeNDIE-ANLIS
> Buenos Aires
> Argentina
> a
>
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>
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