Function predict

On Wed, 2010-07-07 at 20:44 -0300, Luciano Selzer wrote:

Hi Manuel, your problem is that the new variables you created are of numeric
type, while the model was fitted using factor. So the fix is to convert the
new variables to factors so the type matchs

It may need more than that; not tested but I have often run into
problems where I had slightly different levels for factors in the
prediction data than in the fitting.

G

Luciano


2010/7/7 Manuel Spnola <mspinola10 at gmail.com>

Dear list members,

I am fitting a logistic regression with 5 explanatory factors (which I
converted to factors):

mod6 = glm(condicion ~ iluminacion + animales + cielo.raso + piso +
paredes, family=binomial, data=reglog)

I want to obtain the predicted probabilities and the se using the function
"predict" for some combination of the factors.

iluminacion = 1
animales = 0
cielo.raso = 0
piso = 0
paredes = 0

newdata1 = data.frame(iluminacion, animales, cielo.raso, piso, paredes)

newdata1$cond = predict(mod6, newdata = newdata1, type="response")

newdata1$cond = predict(mod6, newdata = newdata1, type="response")

Aviso en model.frame.default(Terms, newdata, na.action = na.action, xlev =
object$xlevels) :
 variable 'iluminacion' is not a factor
Aviso en model.frame.default(Terms, newdata, na.action = na.action, xlev =
object$xlevels) :
 variable 'animales' is not a factor
Aviso en model.frame.default(Terms, newdata, na.action = na.action, xlev =
object$xlevels) :
 variable 'cielo.raso' is not a factor
Aviso en model.frame.default(Terms, newdata, na.action = na.action, xlev =
object$xlevels) :
 variable 'piso' is not a factor
Aviso en model.frame.default(Terms, newdata, na.action = na.action, xlev =
object$xlevels) :
 variable 'paredes' is not a factor
Error: variables 'iluminacion', 'animales', 'cielo.raso', 'piso',  

'paredes'

were specified with different types from the fit

I don't understand what is wrong.
Any help will be appreciated.

Best,

Manuel

--
Manuel Spnola, Ph.D.
Instituto Internacional en Conservacin y Manejo de Vida Silvestre
Universidad Nacional
Apartado 1350-3000
Heredia
COSTA RICA
mspinola at una.ac.cr
mspinola10 at gmail.com
Telfono: (506) 2277-3598
Fax: (506) 2237-7036

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