Univariate data (vector) for which the
potentials shall be estimated
std
Standard deviation of the noise (defaults to
1; this will set scaled potentials)
bw
bandwidth for kernel estimation
weights
optional weights in ksdensity (used by
movpotentials).
grid.size
Grid size for potential estimation.
detection.threshold
maximum detection threshold as
fraction of density kernel height dnorm(0, sd =
bandwidth)/N
bw.adjust
The real bandwidth will be bw.adjust*bw;
defaults to 1
density.smoothing
Add a small constant density
across the whole observation range to regularize density
estimation (and to avoid zero probabilities within the
observation range). This parameter adds uniform density
across the observation range, scaled by
density.smoothing.
detection.limit
ignore maxima that are below
detection.limit * maximum density
Details
Arguments:
Value
livpotential returns a list with the following
elements:
xi
the grid of points on which the potential is
estimated
pot
The estimated potential: -log(f)*std^2/2, where
f is the density.
density
Density estimate corresponding to the
potential.
min.inds
indices of the grid points at which the
density has minimum values; (-potentials; neglecting local
optima)
max.inds
indices the grid points at which the
density has maximum values; (-potentials; neglecting local
optima)
bw
bandwidth of kernel used
min.points
grid point values at which the density
has minimum values; (-potentials; neglecting local optima)
max.points
grid point values at which the density
has maximum values; (-potentials; neglecting local optima)
Author(s)
Based on Matlab code from Egbert van Nes modified by Leo
Lahti. Implemented in early warnings package by V. Dakos.
References
Livina, VN, F Kwasniok, and TM Lenton, 2010. Potential
analysis reveals changing number of climate states during
the last 60 kyr . Climate of the Past, 6, 77-82.
Dakos, V., et al (2012).'Methods for Detecting Early
Warnings of Critical Transitions in Time Series Illustrated
Using Simulated Ecological Data.' PLoS ONE 7(7):
e41010. doi:10.1371/journal.pone.0041010