[R] ace with mon=0

[Christof Schuster]

I was wondering whether someone can help me understand the
following behavior of the ace-function:

When ace is called with mon-parameter set to zero, R gives the
message "response spec can only be lin or ordered
(default)" and returns immediately. However, according to the help
file mon=0 requires the response transformations to be limited
to monotonic transformations.

For instance, the following call of the ace-function will not be
evaluated if one gives mon=0

     TWOPI <- 8*atan(1)
     x <- runif(200,0,TWOPI)
     y <- exp(sin(x)+rnorm(200)/2)
     a <- ace(x,y, mon=0)

Why does mon=0 not work and how should one interpret the message
"the response spec can only be lin or ordered" ?

Any help will be greatly appreciated,
  Christof

Christof Schuster
University of Notre Dame
Department of Psychology                       
103 Haggar Hall
Notre Dame, IN 46556

Tel: (574) 631-5473    email: cschuste at nd.edu
Fax: (574) 631-8883    www.nd.edu/~cschuste