R Dataset / Package robustbase / possumDiv
On this Picostat.com statistics page, you will find information about the possumDiv data set which pertains to Possum Diversity Data. The possumDiv data set is found in the robustbase R package. Try to load the possumDiv data set in R by issuing the following command at the console data("possumDiv"). This may load the data into a variable called possumDiv. If R says the possumDiv data set is not found, you can try installing the package by issuing this command install.packages("robustbase") and then attempt to reload the data with library("robustbase") followed by data("possumDiv"). Perhaps strangley, if R gives you no output after entering a command, it means the command succeeded. If it succeeded you can see the data by typing possumDiv at the command-line which should display the entire dataset.
If you need to download R, you can go to the R project website. You can download a CSV (comma separated values) version of the possumDiv R data set. The size of this file is about 5,236 bytes.
Possum Diversity Data
Possum diversity data: As issued from a study of the diversity of possum (arboreal marsupials) in the Montane ash forest (Australia), this dataset was collected in view of the management of hardwood forest to take conservation and recreation values, as well as wood production, into account.
The study is fully described in the two references.
The number of different species of arboreal marsupials (possum) was
observed on 151 different 3ha sites with uniform vegetation. For each
site the nine variable measures (see below) were recorded.
The problem is to model the relationship between
Two different representations of the same data are available:
The variables have the following meaning:
Eva Cantoni (2004) Analysis of Robust Quasi-deviances for Generalized Linear Models. Journal of Statistical Software 10, 04, http://www.jstatsoft.org/v10/i04
Lindenmayer, D. B., Cunningham, R. B., Tanton, M. T., Nix, H. A. and Smith, A. P. (1991) The conservation of arboreal marsupials in the montane ash forests of the central highlands of victoria, south-east australia: III. The habitat requirements of leadbeater's possum gymnobelideus leadbeateri and models of the diversity and abundance of arboreal marsupials. Biological Conservation 56, 295–315.
Lindenmayer, D. B., Cunningham, R. B., Tanton, M. T., Smith, A. P. and Nix, H. A. (1990) The conservation of arboreal marsupials in the montane ash forests of the victoria, south-east australia, I. Factors influencing the occupancy of trees with hollows, Biological Conservation 54, 111–131.
See also the references in
data(possumDiv) head(possum.mat)str(possumDiv) ## summarize all variables as multilevel factors: summary(as.data.frame(lapply(possumDiv, function(v) if(is.integer(v)) factor(v) else v)))## Following Cantoni & Ronchetti (2001), JASA, p.1026 f.:% cf. ../tests/poisson-ex.R pdFit <- glmrob(Diversity ~ . , data = possumDiv, family=poisson, tcc = 1.6, weights.on.x = "hat", acc = 1e-15) summary(pdFit) summary(pdF2 <- update(pdFit, ~ . -Shrubs)) summary(pdF3 <- update(pdF2, ~ . -eucalyptus)) summary(pdF4 <- update(pdF3, ~ . -Stumps)) summary(pdF5 <- update(pdF4, ~ . -BAcacia)) summary(pdF6 <- update(pdF5, ~ . -aspect))# too much .. anova(pdFit, pdF3, pdF4, pdF5, pdF6, test = "QD") # indeed, ## indeed, the last simplification is too much possumD.2 <- within(possumDiv, levels(aspect)[1:3] <- rep("other", 3)) ## and use this binary 'aspect' instead of the 4-level one: summary(pdF5.1 <- update(pdF5, data = possumD.2))if(FALSE) # not ok, as formually not nested. anova(pdF5, pdF5.1)summarizeRobWeights(weights(pdF5.1, type="rob"), eps = 0.73) ##-> "outliers" (1, 59, 110) wrob <- setNames(weights(pdF5.1, type="rob"), rownames(possumDiv)) head(sort(wrob))
Dataset imported from https://www.r-project.org.
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