Changes in Version 0.9-1

  o new generic functions ORDER() and MATCH() (with
    order() and match() as the default) so that zoo()
    can handle  arbitrary index/time classes when
    suitable methods for the generic function c(),
    length(), order(), match() and subsetting [, are
    supplied.

  o improved printing of "zoo" objects and added
    a summary() method.
    
  o extended coercion functionality to and from
    "zoo" objects. "its" objects can be coerced to
    "zoo" and vice versa. "zoo" objects can be 
    coerced to vector, matrix, data.frame or list.
    
  o added functionality to extract/assign to
    the coredata() of a "zoo" object.
    
  o added/improved functionality to extract/assign
    to the window() of a "zoo" object.
    
  o added/improved functionality to extract/assign
    to the index() or time() of a "zoo" object.
    
  o added lag(), diff(), start(), end(), head(),
    tail() methods.

  o improved plot.zoo() by more flexible expansion
    of plotting parameters such as col, lty and pch.

  o added a cbind() method for "zoo" objects (almost
    synonymous with merge())
  
  o NA handling for "zoo" objects via na.omit(),
    na.contiguous(), na.approx() and na.locf().

  o na.locf() generic function with default method (suitable
    for "zoo" objects) which implements Last Observation
    Carried Forward.
  
  o na.approx() generic function with default method (suitable
    for "zoo" objects) which implements elimination of NAs
    by interpolation.
  
  o added mathematical methods: group generic functions
    for "zoo" objects, t(), cumsum(), cumprod(), cummin(),
    and cummax().

  o added model.frame.AsIs and model.frame.zoo to support
    regression based on zoo objects, in particular with lm()
    (but also many other regression functions).

  o Zero length vector zoo objects may have non-zero index vectors 
    intended to be used in merge to extend zoo objects. zoo
    changed to enable the creation of such objects by omitting
    first argument.

  o added a vignette explaining the new features
  


Changes in Version 0.2-0

  o zoo() now has defaults for both arguments x and order.by,
    which mimic the default behaviour of ts().

  o added new aggregate.zoo() method for computing summary
    statistics of "zoo" objects along a coarser index grid.

  o improved merge.zoo() in three directions:
    1. handling of "zoo" objects with zero columns,
    2. naming of columns in the merged "zoo" object
       which behaves more like merge.data.frame();
       a corresponding suffixes argument has also been added,
    3. introced a fill argument which allows to fill gaps
       by another value than NA.
       
  o improved documentation with extended examples

