These functions extract or change the marks
attached to each of the line segments in the pattern x.
They are methods for the generic functions
marks and marks<-
for the class "psp" of line segment patterns.
The expression marks(x) extracts the marks of x.
The assignment marks(x) <- value assigns new marks to the
dataset x, and updates the dataset x in the current
environment.
The marks can be a vector, a factor, or a data frame.
For the assignment marks(x) <- value, the value
should be a vector or factor of length equal to the number of
segments in x, or a data frame with as many rows
as there are segments in x. If value is a single value,
or a data frame with one row, then it will be replicated
so that the same marks will be attached to each segment.
To remove marks, use marks(x) <- NULL or unmark(x).