Good morning,
I am using R to try to model the proportion of burned area in Portugal.
The dependent variable is the proportion (P). The family used is
binomial and the epsilon would be binary. They have recommended me to
use the Betareg package as it allows to work with proportions.
When I use the Betareg function for my data (2800 lines) with 7
variavels. I created a model using the sum of all seven variables and
using p (proportion of area burnt as the independent variable). I
obtained these results, can you tell me if this is normal? or what do
the errors mean? Thank you in advance.
Is there any limit in the number of lines and variables(columns) to use?
This was the functions used and the results obtained:
>attach(dados)
mod9 <- betareg(P ~
Fuel+Temperature+Slope+Altitude+Precipitation+Roadsproximity+Population,
data=dados)
Warning messages:
1: NaNs produced in: sqrt(W)
2: NaNs produced in: sqrt(W)
3: NaNs produced in: sqrt(1 + phihat)
> summary(mod9)
Call:
betareg(formula = P ~ Fuel + Temperature + Slope + Altitude +
Precipitation + Roadsproximity + Population, data = dados)
Deviance Residuals:
Min. 1st Qu. Median 3rd
0 0 0 0 0
Coefficients:
Estimate Std.Error z-value Pr(>|z|)
(Intercept) -83062.5 9.34E-02 -8.89E+05 0
FuelAnnualCrop -2256.8 2.31E-01 -9.78E+03 0
FuelHard
-8179.8 7.95E-02 -1.03E+05 0
FuelHardSoftEuc -4449.7 7.02E-02 -6.34E+04 0
FuelNoFuel -9552.1 9.02E-02 -1.06E+05 0
FuelPermCrop -5112.5 8.39E-02 -6.10E+04 0
FuelShrubs -8246 7.32E-02 -1.13E+05 0
FuelSoft
-11795.1 7.51E-02 -1.57E+05 0
FuelSoftEuc -1561.8 7.67E-02 -2.04E+04 0
Temperature -1.3E+07 7.14E-04 -1.80E+10 0
Slope
78122.8 3.78E-03 2.07E+07 0
Altitude
1143023 7.19E-05 1.59E+10 0
Precipitation -1482288 2.11E-03 -7.03E+08 0
RoadsproximityDistRd>1Km -45315.1 3.82E-02 -1.19E+06 0
Population 4711684 2.81E-04 1.68E+10 0
Estimated precision parameter (phi): -560353.4 with s.e. 315.9113
Null Deviance: 0 on 2818 degrees of freedom
Residual Deviance: 0 on 2804 degrees of freedom
Log-Likelihood Ratio Statistic: 3291846935 on 14 degrees of freedom
Pseudo R^2: 0.07753642 AIC: -3291849573
Warning messages:
1: NaNs produced in: sqrt(muhat * (1 - muhat)/(1 + phihat))
2: NaNs produced in: sqrt(muhat * (1 - muhat)/(1 + phihat))
Thank you very much in advance,
Jordi
>
--
______________________________________________________________________
Jordi Garcia-Gonzalo
FORCHANGE - Forest Ecosystem Management Under Global Change
Departamento de Engenharia Florestal - Instituto Superior de Agronomia
Universidade Técnica de Lisboa
Tapada da Ajuda, 1349-017 Lisboa
Portugal
tel: +351 21 365 33 66
fax: +351 21 364 50 00
email:[EMAIL PROTECTED]
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