From: Jan Verbesselt <Jan.Verbesselt_at_biw.kuleuven.be>

Date: Sat 16 Apr 2005 - 00:43:31 EST

**NDWI''' -190.566 254.590 -0.75 0.4541
**
When analysing the glm fit of the same model

ir. Jan Verbesselt

Research Associate

Lab of Geomatics Engineering K.U. Leuven Vital Decosterstraat 102. B-3000 Leuven Belgium Tel: +32-16-329750 Fax: +32-16-329760

http://gloveg.kuleuven.ac.be/

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat Apr 16 00:47:56 2005

Date: Sat 16 Apr 2005 - 00:43:31 EST

Dear,

When fitting the following model

knots <- 5

lrm.NDWI <- lrm(m.arson ~ rcs(NDWI,knots)

I obtain the following result:

lrm(formula = m.arson ~ rcs(NDWI, knots))

Frequencies of Responses

0 1

666 35

Obs Max Deriv Model L.R. d.f. P C Dxy Gamma Tau-a R2 Brier 701 5e-07 34.49 4 0 0.777 0.553 0.563 0.053 0.147 0.045 Coef S.E. Wald Z P Intercept -4.627 3.188 -1.45 0.1467 NDWI 5.333 20.724 0.26 0.7969 NDWI' 6.832 74.201 0.09 0.9266 NDWI'' 10.469 183.915 0.06 0.9546

Call: glm(formula = m.arson ~ rcs(NDWI, knots), x = T, y = T)

Coefficients:

(Intercept) rcs(NDWI, knots)NDWI rcs(NDWI, knots)NDWI' rcs(NDWI, knots)NDWI'' rcs(NDWI, knots)NDWI'''

0.02067 0.08441 -0.54307 3.99550 -17.38573 Degrees of Freedom: 700 Total (i.e. Null); 696 Residual Null Deviance: 33.25 Residual Deviance: 31.76 AIC: -167.7

A negative AIC occurs!

How can the negative AIC from different models be compared with each other? Is this result logical? Is the lowest AIC still correct?

Thanks,

Jan

ir. Jan Verbesselt

Research Associate

Lab of Geomatics Engineering K.U. Leuven Vital Decosterstraat 102. B-3000 Leuven Belgium Tel: +32-16-329750 Fax: +32-16-329760

http://gloveg.kuleuven.ac.be/

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat Apr 16 00:47:56 2005

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