Changes in Version 2.2-5
o Bug fix in C code.
Changes in Version 2.2-4
o Minor documentation update.
Changes in Version 2.2-3
o Bug fix for old releases of R.
o A .Rnw file have been added in the new folder 'vignettes' to generate the PDF already in
'inst/doc'.
Changes in Version 2.2-2
o The argument 'initbh' in strata.LH() and the argument 'nclass' in strata.cumrootf() have
been changed position.
o The behaviour of Kozak's algorithm for exception cases have been improved (warning
generated, NaN values in the output and the print).
o Changes in parameter default values:
* 'takeall.adjust' in strata.bh() is now TRUE by default, which is more consistent
with the rest of the package;
* the 'minsol' element in 'algo.control' now has the default value 10 000 instead of
1000 since the complete enumeration is now coded in C, thus it runs faster;
* the 'maxstep' element in 'algo.control' now has a larger default value: \code{Nu/10},
rounded up and truncated to 100 (Nu is the number of unique values in the x-vector
from which units in the certainty stratum, if any, have been removed);
* the 'maxstill' element in 'algo.control' now has a smaller default value because
it was unnecessarily large (which increased Kozak's algorithm computational time):
new default = maxstep*10, bounded between 50 and 500.
o In Kozak's algorithm, the value of 'maxstep' and 'maxstill' are now brought down to 3
and 50, respectively, when new boundaries are accepted under certain circumstances
(see help(strata.LH)). It allows the algorithm to run much faster because it needs
less iterations to converge.
o Sethi's algorithm: when a non requested take-all stratum appears at the end of the
algorithm run, the algorithm is run again starting from the boundaries at the end of
the preceding run instead of starting at 'initbh'.
o Change in strata.LH() output values: run.min, niter and sol.min can now be vectors
because more than one run of the algorithm and, less frequently, more than one
possible sets of boundaries can lead to the optimal solution.
o General change in the output values: nh.nonint has been renamed nhnonint.
o A vignette has been added in the package.
o var.strata() now returns nhnonint.
o Correction of an error introduced in version 2.2-0 in the calculation of the output
values relativebias and propbiasMSE.
o The option 'trymany=TRUE' have been improved.
o The arguments 'takeall' and 'takenone' can now be logical objects.
Changes in Version 2.2-1 (non public version)
o Bug fixes for the exception cases of null stratum variances and takeall stratum larger
than a target n.
Changes in Version 2.2-0 (non public version)
o Major code restructuring. Some features originally coded in R have been translated in C
to make strata.LH() faster.
o By default, strata.LH() runs Kozak's algorithm with three different sets of initial
boundaries: cumulative root frequency, geometric and robust ones. This option is
controlled with the new 'algo.control' element 'trymany' (see help(strata.LH) for more
information). This default behaviour helps getting good and consistent results. Before
this version, it was problematic to have a default behaviour running the algorithm many
times because it was long to run. It can now run pretty quickly because of the code
improvement done.
o The modified Kozak's algorithm, which is a non-random version of Kozak's algorithm, is
no more available because it never performed as well as the original Kozak's algorithm
in our numerical experiments. Therefore, the 'algo.control' element 'method' has been
dropped.
o For Kozak's algorithm, when initial boundaries do not meet the conditions Nh >= minNh
and nh>0, they are not replaced by robust boundaries anymore. Instead, a warning is
printed and the algorithm is not run.
o Changes in strata.LH() output values:
* the output value initbh has been removed (one can see which initial boundaries has
been used in the output value args$initbh);
* opti.criteria was always opti.nhnonint, this have been corrected;
* rep.detail and rep.min have been renamed run.detail and run.min;
* iter.detail, run.detail and sol.detail has been improved: among others, in
sol.detail the boundaries are now obtained by averaging two consecutive unit values
instead of taking the value of a unit;
* nsol is now always provided for Kozak's algorithm.
o General changes in the output values:
* the 'args' list output by every public function of the package has been improved;
* the elements order has been improved;
* the takeall value was sometime incorrect, it has been corrected.
o Changes in the print of objects of class 'strata':
* information about stratum type has been added;
* some column names have been shortened in the table;
* in the 'Given arguments' section, the algo.control elements have been improved;
* for objects produce with strata.LH() with the option 'trymany=TRUE', the initial
boundaries are not printed anymore.
o Bug fixes concerning the certainty stratum (target n now reached correctly, n includes
the certainty stratum).
Changes in Version 2.1-2
o In version 2.1-1, the default values for the algorithm parameters in strata.LH made
the function long to run. They have been modified by values giving almost as often
optimal solution and running faster. The default value for the parameter maxstep now
equals 3 for the modified Kozak's algorithm and pmin(ceiling(Nu/15),75) for the
original one, where Nu stands for the number of unique values in the input data
(without considering the units in the certainty stratum). The default value for maxstill
now takes into account the value of maxstep. It is calculated with the command:
floor(maxstep*100/3). Also, by default, rep now equals 5 instead of 3. In the next
version of the package, the function strata.LH should be even faster and give better
results with its arguments' default values.
o For Kozak's algorithm, the default initial stratum boundaries are now obtained with
the cumulative root frequency method instead of using initial boundaries forming strata
of equal sizes, called arithmetic boundaries (see help(strata.LH) for justifications).
The default value of 'initbh' remains unchanged for Sethi's algorithm.
o The way the best repetition of the original Kozak's algorithm is chosen has been
improved. If many repetition lead to the same minimal opti.nh criteria, the repetition
leading to the smallest opti.nhnonint criteria is chosen.
o The examples in the help pages have been modified a little to insure that they are not
too long to run.
Changes in Version 2.1-1
o The default values for the algorithm parameters in strata.LH have been changed for
values giving typically an equivalent or better solution than the previous default
algorithm parameters. They are now (initbh="nh", maxstep=6, rep="change"). They used
to be (initbh="nhnonint", maxstep=3, rep=3). This change affects the execution time of
the function. It is much slower. The next version of the package should improve this.
o The 'Given arguments' section of the print for an object of class 'strata' has been
improved.
o Minor bug fixes in strata.LH.
Changes in Version 2.1-0 (non public version)
o Prior to this version, the optimization criteria (criteria=RRMSE for a given n
and criteria=n for a given CV) was always calculated with non-integer stratum
sample sizes, called nhnonint (obtained directly from applying the allocation rule,
see help(stratification)). The output contained integer sample sizes, called nh, but
these were not considered in the optimization criteria calculation. For Kozak's
algorithm, it is now possible to choose which sample sizes are used to calculate
the optimization criteria : integer or non-integer ones.
o In 'algo.control', the element 'idopti' has been added. This parameter determines which
stratum sample sizes are going to be used to calculate the optimization criteria.
It can take the value "nh" (criteria calculated with the integer sample sizes nh)
or "nhnonint" (criteria calculated with the non-integer sample sizes nhnonint).
The default value is "nh" since it gives slightly better results than idopti="nhnonint"
and also because the integer sample sizes are the ones used in practice. This parameter
is used by Kozak's algorithms only.
o When a complete enumeration is performed, the criteria is automatically calculated with
integer stratum sample sizes.
o Because Sethi's algorithm works with derivatives to perform optimization, it can only use
a real optimization criteria, i.e. the one calculated with the non-integer sample sizes.
o The output value opti.criteria has been replaced by two values, opti.nh and opti.nhnonint,
for the functions strata.bh(), strata.geo(), strata.cumrootf(). The value opti.nhnonint is in
fact equal to the old opti.criteria. Only the name has changed. It is still the criteria
to optimize calculated with the non integer stratum sample sizes (nhnonint). The value
opti.nh is the same criteria, but calculated with the integer sample sizes (nh). For the
function strata.LH, the output value opti.criteria still exists, but its value now depends
on the new 'algo.control' element 'idopti'. If idopti="nh", opti.criteria is the criteria
to optimize calculated with the integer nh. If idopti="nhnonint", opti.criteria is the
criteria to optimize calculated with the non-integer nhnonint.
Changes in Version 2.0-4
o A warning is now printed when Kozak's algorithm is not able to move (when it discards
every updated boundaries and remains at the initial boundaries).
o Bug fixes for the extreme case of a null optimization criteria for the initial boundaries.
o Bug fixes in the internal function optiCriteria and the C function strataC. In extreme
cases, the quantity V2 + (U / (n - T1)) - V3 - V4 could be negative. Therefore, taking
its square root returned NaN, which caused problem later on. This quantity is now
truncated to zero.
Changes in Version 2.0-3
o Useless files have been deleted from the package source.
Changes in Version 2.0-2
o Minor correction in plot.strata when a certainty stratum is included in the strata object.
o Bug fixes for the function strata.cumrootf for some rare cases.
o The function var.strata now applies the posterior correction for non-response to the
non integer stratum sample sizes.
o The function plot.var.strata now prints correctly the loglinear model parameters.
o The function plot.strata now prints "model = complete enumeration" if a complete
enumeration was carried out.
o Minor modifications to the documentation.
Changes in Version 2.0-1
o Bug fixes for the function strata.LH concerning the modification of initial stratum
boundaries if they do not meet the condition Nh>=minNh and nh>0.
Changes in Version 2.0-0
o First CRAN release of the stratification package.