integer vector of length two;
the maximum number of lags at which to estimate the autocorrelation.
If it is not supplied, it is an integer proportional to the logarithm of the
row length, or a vector of two integers proportional to the logarithms
of the row and column lengths.
type
a character string:
"covariance" to estimate the autocovariance function;
"correlation" for the autocorrelation function.
plot
logical flag, if
TRUE, the 2D autocorrelation function will be plotted.