Create a grid of time spent from an object of class trip by exact
cell crossing methods, weighted by the time between locations for separate
trip events.
tripGrid(x, grid = NULL, method = "pixellate", ...)object of class trip
GridTopology - will be generated automatically if NULL
pixellate or density
pass arguments to density.psp if that method is chosen (and
temporary mechanism to direct users of legacy methods to
tripGrid.interp)
tripGrid returns an object of class SpatialGridDataFrame, with
one column "z" containing the time spent in each cell in seconds.
Zero-length lines cannot be summed directly, their time value is summed by assuming the line is a point. A warning used to be given, but as it achieved nothing but create confusion it has been removed. The density method returns proportionate values, not summed time durations.
See pixellate.psp and pixellate.ppp for the details on the
method used. See density.psp for method="density".
Trip events are assumed to start and end as per the object passed in. To
work with inferred "cutoff" positions see split.trip.exact.