The function nmf.equal tests if two NMF models are
  the same, i.e. they contain -- almost -- identical data:
  same basis and coefficient matrices, as well as same
  extra parameters.
nmf.equal(x, y, ...) S4 (NMF,NMF) `nmf.equal`(x, y, identical = TRUE, ...) S4 (list,list) `nmf.equal`(x, y, ..., all = FALSE, vector = FALSE)
nmf.nmf.identical (TRUE) or
  all.equal (FALSE). See description
  for method nmf.equal,NMF,NMF.all=TRUE,
  that indicates if all fits must be equal for x and
  y to be declared equal, or if one wants to return
  the result of each comparison in a vector.nmf.equal compares two NMF models, and return
  TRUE iff they are identical acording to the
  function identical when
  identical=TRUE, or equal up to some tolerance
  acording to the function all.equal. This
  means that all data contained in the objects are
  compared, which includes at least the basis and
  coefficient matrices, as well as the extra parameters
  stored in slot misc.
If extra arguments are specified in ..., then the
  comparison is performed using all.equal,
  irrespective of the value of argument identical.
signature(x = "NMF", y = "NMF"):
  Compares two NMF models.
  
      Arguments in ... are used only when
  identical=FALSE and are passed to
  all.equal.
signature(x = "NMFfit", y =
  "NMF"): Compares two NMF models when at least one comes
  from a NMFfit object, i.e. an object returned by a single
  run of nmf.
  
      signature(x = "NMF", y =
  "NMFfit"): Compares two NMF models when at least one
  comes from a NMFfit object, i.e. an object returned by a
  single run of nmf.
  
      signature(x = "NMFfit", y =
  "NMFfit"): Compares two fitted NMF models, i.e. objects
  returned by single runs of nmf.
  
      signature(x = "NMFfitX", y =
  "NMF"): Compares two NMF models when at least one comes
  from multiple NMF runs.
  
      signature(x = "NMF", y =
  "NMFfitX"): Compares two NMF models when at least one
  comes from multiple NMF runs.
  
      signature(x = "NMFfitX1", y =
  "NMFfitX1"): Compares the NMF models fitted by multiple
  runs, that only kept the best fits.
  
      signature(x = "list", y =
  "list"): Compares the results of multiple NMF runs.
  
      This method either compare the two best fit, or all fits
  separately. All extra arguments in ... are passed
  to each internal call to nmf.equal.
signature(x = "list", y =
  "missing"): Compare all elements in x to
  x[[1]].