frogs | R Documentation |

The `frogs`

data frame has 212 rows and 11 columns.
The data are on the distribution of the Southern Corroboree
frog, which occurs in the Snowy Mountains area of New South Wales,
Australia.

`frogs`

This data frame contains the following columns:

- pres.abs
0 = frogs were absent, 1 = frogs were present

- northing
reference point

- easting
reference point

- altitude
altitude , in meters

- distance
distance in meters to nearest extant population

- NoOfPools
number of potential breeding pools

- NoOfSites
(number of potential breeding sites within a 2 km radius

- avrain
mean rainfall for Spring period

- meanmin
mean minimum Spring temperature

- meanmax
mean maximum Spring temperature

Hunter, D. (2000) The conservation and demography of the southern corroboree frog (Pseudophryne corroboree). M.Sc. thesis, University of Canberra, Canberra.

```
print("Multiple Logistic Regression - Example 8.2")
plot(northing ~ easting, data=frogs, pch=c(1,16)[frogs$pres.abs+1],
xlab="Meters east of reference point", ylab="Meters north")
pairs(frogs[,4:10])
attach(frogs)
pairs(cbind(altitude,log(distance),log(NoOfPools),NoOfSites),
panel=panel.smooth, labels=c("altitude","log(distance)",
"log(NoOfPools)","NoOfSites"))
detach(frogs)
frogs.glm0 <- glm(formula = pres.abs ~ altitude + log(distance) +
log(NoOfPools) + NoOfSites + avrain + meanmin + meanmax,
family = binomial, data = frogs)
summary(frogs.glm0)
frogs.glm <- glm(formula = pres.abs ~ log(distance) + log(NoOfPools) +
meanmin +
meanmax, family = binomial, data = frogs)
oldpar <- par(mfrow=c(2,2))
termplot(frogs.glm, data=frogs)
termplot(frogs.glm, data=frogs, partial.resid=TRUE)
cv.binary(frogs.glm0) # All explanatory variables
pause()
cv.binary(frogs.glm) # Reduced set of explanatory variables
for (j in 1:4){
rand <- sample(1:10, 212, replace=TRUE)
all.acc <- cv.binary(frogs.glm0, rand=rand, print.details=FALSE)$acc.cv
reduced.acc <- cv.binary(frogs.glm, rand=rand, print.details=FALSE)$acc.cv
cat("\nAll:", round(all.acc,3), " Reduced:", round(reduced.acc,3))
}
```