any rectangular time series object which can be converted by the
function as.matrix() into a matrix object, e.g. like an
object of class timeSeries, data.frame, or mts.
bins
an integer value, the number of bins used for the biariate
histogram.
method
a character string denoting whic h type of binning should be
used, either "squared" or "hexagonal".
...
optional arguments to be passed.
References
Wuertz, D., Chalabi, Y., Chen W., Ellis A. (2009);
Portfolio Optimization with R/Rmetrics,
Rmetrics eBook, Rmetrics Association and Finance Online, Zurich.