Leadbeater's Possums

Abundance of Leadbeater's Possums observed in the field.

Usage

data(lpossums)

Format

A data frame with the following variables.

number

Values between 0 and 10 excluding 6.

ofreq

Observed frequency, i.e., the number of sites.

Details

A small data set recording the abundance of Leadbeater's Possums Gymnobelideus leadbeateri observed in the montane ash forests of the Central Highlands of Victoria, in south-eastern Australia. There are 151 3-hectare sites. The data has more 0s than usual relative to the Poisson, as well as exhibiting overdispersion too.

Source

Welsh, A. H., Cunningham, R. B., Donnelly, C. F. and Lindenmayer, D. B. (1996). Modelling the abundances of rare species: statistical models for counts with extra zeros. Ecological Modelling, 88, 297–308.

See also

zipoissonff.

Examples

lpossums
#>    number ofreq
#> 1       0    95
#> 2       1     9
#> 3       2    10
#> 4       3    12
#> 5       4     8
#> 6       5     9
#> 7       7     4
#> 8       8     1
#> 9       9     1
#> 10     10     2
(samplemean <- with(lpossums, weighted.mean(number, ofreq)))
#> [1] 1.370861
with(lpossums,  var(rep(number, times = ofreq)) / samplemean)
#> [1] 3.731143
sum(with(lpossums, ofreq))
#> [1] 151
if (FALSE)  spikeplot(with(lpossums, rep(number, times = ofreq)),
  main = "Leadbeater's possums", col = "blue", xlab = "Number")  # \dontrun{}