Package intRvals calculates means and variances of arrival intervals (and arrival rates) corrected for missed arrival observations, and compares means and variances of groups of interval data.
Installation in R
The central function of package
estinterval, which is used to estimate the
mean arrival interval (and its standard deviation) from interval data with missed arrivals. This is
achieved by fitting the theoretical probability density
intervalpdf to the interval data
The package can be used to analyse general interval data where intervals are derived from distinct arrival observations. For example, the authors have used it to analyze dropping intervals of grazing geese for estimating their faecal output.
Intervals are defined as the time between observed arrival events (e.g. the time between one excreted droppings to the next) The package provides a way of taking into account missed observations (e.g. defecations), which lead to occasional observed intervals at integer multiples of the true arrival interval.
- Fit interval model
mto an interval dataset
estinterval, as in
- Visually inspect model fits using
plot.intRvals, as in
anova.intRvalsto check whether the missed event probability was signficantly different from zero, as in
- Also use
anova.intRvalsto perform model selection between competing models
m2for the same interval dataset
d, as in
- Compare means and variances between different interval datasets
Other useful functionality
foldprovides functionality to fold observed intervals back to their fundamental interval
fundamentaltests which intervals are fundamental, i.e. intervals not containing a missed arrival observation
interval2rateconverts interval estimates to rates
partitionestimates and tests for the presence of within-subject variation
intervalsimsimulates a set of observed intervals
The package comes with a example interval dataset
- Dokter, A.M., et al. 2017. Analysing time-ordered event data with missed observations, Ecology and Evolution, 2017, in press.
- Bédard, J. & Gauthier, G. 1986. Assessment of faecal output in geese. Journal of Applied Ecology, 23, 77-90.
- Owen, M. 1971. The Selection of Feeding Site by White-Fronted Geese in Winter. Journal of Applied Ecology 8: 905-917.