Assess the significance of spatial early-warning values
indictest(x, nperm = 999, ...)A spatial warning object such as one produced by the *_sews
function family
The number of permutations to carry out to produce the null distribution
Additional arguments passed to methods
An object of class *_sews_test depending on the input object
(actually, a data.frame)
The significance of many early-warning signals can be estimated by reshuffling the original matrix. Indicators are then recomputed on the shuffled matrices and the values obtained are used as a null distribution. P-values are obtained based on the rank of the observered value in the null distribution.
Kefi, S., Guttal, V., Brock, W.A., Carpenter, S.R., Ellison, A.M., Livina, V.N., et al. (2014). Early Warning Signals of Ecological Transitions: Methods for Spatial Patterns. PLoS ONE, 9, e92097