Changes in Version 0.4.4-6
  
  o fixed the '`class(.) == *`'  issue

  o changed pairwise specific object class for results from functions pairwise.person.fit() and pairwise.item.fit() to 'pifit' and 'ppfit' respectively

  o changed pairwise specific object class for results from function pairwise.S() 'pairS'

Changes in Version 0.4.4-5.3
  
  o fixed a minor bug in (deprecated) internal function 'pvx.super' 

Changes in Version 0.4.4-5.2
  
  o added citation information

Changes in Version 0.4.4-5.1
  
  o changed internal datapreperation tasks to keep the order of person (estimates) for output.

Changes in Version 0.4.4-4
  
  o extended the main function 'pair()' to use case weights for item parameter calculation.
  
Changes in Version 0.4.4-3
  
  o changed internal datapreperation tasks (rownames for persons).
  
  o changed: pairwise will globaly change 'options(stringsAsFactors = FALSE)' when applying 'pair()' or 'pers()'
  
Changes in Version 0.4.4-2
  
  o fixed (changed) summary funtion for objects of class 'pairwise.person.fit'.

  o extended function Q() with two arguments to compute the Q person-fit-index based on response data and threshold parameters.

Changes in Version 0.4.4-1

  o cleaned up in function Q() to compute the Q person-fit-index proposed by Tarnai and Rost (1990).

Changes in Version 0.4.3-1

  o added function Q() to compute the Q person-fit-index proposed by Tarnai and Rost (1990).

Changes in Version 0.4.2-1

  o added function q3() to compute Yen's Q3 fit statistic.
  
  o changed structure of result object of function rfa().

Changes in Version 0.4.2-1

  o fixed a bug in function ptbis().

Changes in Version 0.4.2

  o enhanced plotting method for object of class "pers".

  o added function pairwise.S() to perform the Fischer-Scheiblechner statistic 'S'; a 'Wald like test' on item level. 
  
 Changes in Version 0.4.1

  o added function deltapar() to compute delta or rather item step parameters from thurstonian threshold parameters.
    
  o added argument p in function logLik.pers().

 Changes in Version 0.4.0

  o fixed minor bug in function pers() relating to passing throug arguments from "pair" object under special data situations.
 
  o fixed minor bug in function andersen.pers() concerning reading arguments from "pers" object.
 
 Changes in Version 0.3.2

  o further enhancements.
 
  o fixed a minor bug in function gif().
   
  o fixed a minor bug in plotting methods for item parameters.

Changes in Version 0.3.0

  o added wighted Likelihood in result object of function pers().
 
  o added summary function for pairwise.person.fit().
  
  o added summary function for pairwise.item.fit().

  o added function simra().

  o added function andersentest.pers().

  o added covariate data to the bfiN and bfiN_miss data sets.

  o added logical option itemNames = 'TRUE / FALSE' in ploting method for objects of class "pers". 

  o changed structure of result in pairSE() and changed depending functions.

  o added the function lrtest.pers() to perform a likelihood ratio test against the saturated model  for object of class "pers"

  o changed internal calculations for powers of the pairwise comparison matrix.

  o make use of transpose logical in S3 method for rfa - plot.rfa().

  o extended options of argument pot in func. pair().

  o fixed a bug in S3 method logLik.pers when calculating the degrees of freedom.


Changes in Version 0.2.5

  o added the S3 method logLik.pers to extract the Log-Likelihood for object of class "pers"

  o added the function rfa() and its plotting and summary S3 method to perfom rasch residual factor analysis proposed by Wright (1996) and further discussed by Linacre (1998).

  o added the function iff() to plot or return values for Item Information Function.

  o added the function tff() to plot or return values for Test Information Function.

  o added two example dataset (kft5 and Neoffi) used in Rost (2004).

  o added an optional argument in function pers() for calculation of the WLE reliability.

  o changed spliting argument in function grm() and changed S3 methods plot and summary for objects of class "grm"

  o fixed a minor bug in S3 method plot.grm when defining axis annotation 

  o fixed a error messages which occured under extreme sparse data situations using function pers()


Changes in Version 0.2.4

  o fixed a mismatch when calcualting item and person fit statistic under booklet design circumstances
  o fixed some error messages which occur under extreme sparse data situations in some internal functions.
  o added WLE Reliability in object of class "pers".

  o changed summary method for object of class "pers".

  o added plotting method for object of class "pers" and documentation. This plots a person item map. 


Changes in Version 0.2.2

  o added main function pair() for item parameter calculation for dicho- or polytomuous data . Data with unequal number of categories for items can be processed. 

  o added main function pers() for person parameter (WLE) calculation for dicho- or polytomuous data. Data with unequal number of categories for items can be processed. 

  o added function ptbis() for calculation of point biserial correlations for dicho- or polytomous item categories with total scale.

  o added person - pairwise.person.fit() - and item - pairwise.item.fit() - fit indices. 

  o added function for tabulation of response data - ftab(). 

  o added function for expected score curves plots - esc().

  o added function for category probability plots - catprob(). 

  o added function for graphical item fit by empirical category probability plots - gif().

  o added another (small) example dataset sim200x3, containing simulated Data with one dichotomous and two polytoumous items with 200 observations.

  o added a (large) example data structure DEU_PISA2012 - for a detailed description of the data structure see the section User guides, package vignettes and other documentation.

  o changed the plotting methods for "pair"", "grm" and "pairSE" and added documentation for them.

  o removed deprecated functions (from version 0.1.5): 
itempar.dicho(), itempar.poly(), grmSE.dicho(), grmSE.poly(), ipSE.dicho(), ipSE.poly(), ppML.dicho(), ppWL.dicho(), thetaML.dicho(), thetaWL.dicho, ptbis.dicho(). 
Those functions are therefore only available in older version of pairwise in the CRAN archive.

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Changes in Version 0.1.5

  o added function for Point Biserial Correlations ptbis.dicho() (dicotoumous items)

  o added function for handling booklet designs make.incidenz()

  o added functions for person parameter estimation (ML & WL) and summary method (dicotoumous items)

  o added summary method for graphical model-check dichotomuos (object of class "grmSE")

  o added summary method for graphical model-check polytomuos (object of class "grmSEpo")


Changes in Version 0.1.4

  o added the argument zerocor in the functions for parameter calculations - see descriptions of functions

  o changed some matrix calculations to enhance processing speed (due to a tip from Alexander Robitzsch)

