An object of class "ppx" (see ppx)
  represents a marked point pattern
  in multidimensional space and/or time. There may be any
  number of spatial coordinates, any number of temporal coordinates,
  and any number of mark variables. The individual marks may be
  atomic (numeric values, factor values, etc) or objects of any kind.
The function as.hyperframe.ppx extracts the coordinates
  and the marks as a "hyperframe" (see
  hyperframe) with one row of data for each
  point in the pattern. This is a method for the generic
  function as.hyperframe.
The function as.data.frame.ppx discards those mark variables
  which are not atomic values, and extracts the coordinates
  and the remaining marks as a data.frame
  with one row of data for each
  point in the pattern. This is a method for the generic
  function as.data.frame.
Finally as.matrix(x) is equivalent to
  as.matrix(as.data.frame(x)) for an object of class
  "ppx". Be warned that, if there are any columns of non-numeric
  data (i.e. if there are mark variables that are factors),
  the result will be a matrix of character values.