constructor for data given as 2 column data.frame
# S4 method for data.frame,missing,missing,missing,missing
ScalarTimeMap(map, lag = 0, interpolation = splinefun)
object of class:data.frame
, In this case a data.frame. Only the first two columns will be
used
a (scalar) delay
the interpolation, usually splinefun or approxfun