mSynch function

The mean (cross-)correlation (with bootstrapp CI) for a panel of spatiotemporal data

mSynch is the function to estimate the mean (cross-)correlation in a spatiotemporal dataset as discussed in Bjornstad et al. (1999). The function requires multiple observations at each location.

mSynch(x, y = NULL, resamp = 999, na.rm = FALSE, circ = FALSE, quiet = FALSE)

Arguments

• x: matrix of dimension n x p representing p observation at each location (i.e. each row is a time series).
• y: optional matrix of dimension m x p representing p observation at each location (i.e. each row is a time series). If provided, the mean cross-correlation between the two panels is computed.
• resamp: the number of resamples for the bootstrap or the null distribution.
• na.rm: If TRUE, NA's will be dealt with through pairwise deletion of missing values for each pair of time series -- it will dump if any one pair has less than two (temporally) overlapping observations.
• circ: If TRUE, the observations are assumed to be angular (in radians), and circular correlation is used.
• quiet: If TRUE, the counter is suppressed during execution.

Returns

An object of class "mSynch" is returned, consisting of a list with two components: - real: the regional average correlation.

• boot: a vector of bootstrap resamples.

Details

Missing values are allowed -- values are assumed missing at random.

The circ argument computes a circular version of the Pearson's product moment correlation (see cor2).

Examples

# first generate some sample data
x <- expand.grid(1:20, 1:5)[, 1]
y <- expand.grid(1:20, 1:5)[, 2]
# z data from an exponential random field
z <- cbind(
  rmvn.spa(x = x, y = y, p = 2, method = "exp"), 
  rmvn.spa(x = x, y = y, p = 2, method = "exp")
  )

# mean correlation analysis
fit1 <- mSynch(x = z, resamp = 500)
print(fit1)

References

Bjornstad, O.N., Ims, R.A. & Lambin, X. (1999) Spatial population dynamics: Analysing patterns and processes of population synchrony. Trends in Ecology and Evolution, 11, 427-431. doi:10.1016/S0169-5347(99)01677-8

See Also

print.mSynch

Author(s)

Ottar N. Bjornstad onb1@psu.edu