Version 0.18

* Improved method for `rbind()` data frames, taking care of declared variables
* Function value_labels() has been replaced with the generic base function
  `labels()`, and the function `variable_label()` has been replaced with the
  function `label()`
* Changed default for `as.factor()`, with values and (where available) levels
  (thanks to Daniel Antal for the report)
* New generic function `drop_na()` to drop information about the declared
  missing values

Version 0.17

* Correctly determine the object mode, function of both value labels and
  input values (especially when all input values are empty NA values)
* New argument "`measurement`" in function `declared()`
* New function `measurement()`, to query and allocate measurement levels

Version 0.16

* New logical argument "`values`" in the S3 method for `as.character()`
* Removed aliases `as_declared()` and `as_haven()` from the namespace
* Fixed `as.haven()` which should return double objects

Version 0.15

* Class method for many / most primitive functions, with declared objects
* Bug fix in `w_table()` affecting zero frequency categories
* Dropped alias `frtable()` from function `w_table()`
* New function `is.empty()`, testing the presence of undeclared missing values
* Main function `declare()` is now generic, allowing flexibility to create
  custom methods for any other classes of objects
* Removed dependency on package admisc, by incorporating the necessary
  functionality as internal functions

Version 0.13

* New functions `w_mode()` and `w_standardize()`
* Fixed `w_summary()`, summaries should not be rounded by default
* Fixed `w_mean()` to weight negative values
Thanks to an anonymous reviewer for reporting and suggesting the following:
* New argument "`drop`" in function `undeclare()`
* Bug fix in the class methods for `head()` and `tail()`
* Function declared now duly recognizes input factors
* Extended `as.factor()` for objects of class "`declared`"
* Added proper class methods for primitive arithmetic operations
* New functions `as.declared()`, `is.declared()`
* Added explanatory documentation (for instance in the DESCRIPTION file) to
  explain the reasons for reimplementing some of the base functions

Version 0.12

* New function `w_summary()`
* Functions `w_table()` and `w_quantile()` now properly deal with missing weights
* New argument "`trim`" in function `w_mean()`

Version 0.11

* Fixed `w_table()`, an internal object was inadvertently returned
* Improved printing of crosstables

Version 0.10

* New functions `w_mean()`, `w_var()` and `w_sd()`, `w_quantile()` and
  `w_median()`, to  obtain weighted versions of mean, variance and standard
  deviation, quantiles and median, respectively, adapted to declared objects
* Fixed a bug in `as.haven.declared()`, when all values are (declared)
  missing and labels are not numeric
* Argument "`weight`" changed to "`wt`" in `w_table()`
* New arguments in function `w_table()`: "`observed`" to only print observed
  values, and "`margin`" to calculate proportions in crosstabs
* Function `w_table()` now accepts a second argument "`y`" to create crosstabs
* Function `frtable()` renamed to `w_table()` standing for weighted table

Version 0.9

* New argument "`weight`" in function `frtable()`, allowing to weight not
  only valid but also missing values
* More robust function `frtable()` in treating declared values with
  overlapping labels (e.g. hierarchical ISCO codes and categories)
* Fixed a bug in `declared()` when all values are completely missing

Version 0.8

* Improved treatment of equality and non-equality, now accepting labels as
  well as values
* Reverted functionality to not dropping the attributes in arithmetic
  operations, this is now left to the users' preference

Version 0.7

* Bug fix saving declared data frames as .csv files
* `as.declared()` now retains the "format.spss" attribute, if existing

Version 0.6

* Improved treatment of arithmetic operations, attributes are no longer
  propagated (thanks to Randall Pruim for the suggestion)
* Modified as.haven() for objects of class "`declared`", to avoid a bug in
  package ReadStat that prevents exporting missing values to SPSS for
  integer variables

Version 0.5

* Initial version