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help for ^centcalc^                                          (STB-34 sbe13)
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Centile calculation
-------------------

   ^centcalc^ mvar svar[^,^ ^c^entiles^(^cent_list^) di^st^(n^|^en^|^men^|^pn^|^mpn^|^sl)^
	^g^amma^(^#|gvar^) de^lta^(^#|dvar^) cv p^refix^(^stub^)^ ]


Description
-----------

^centcalc^ calculates distribution-based centiles from user-supplied parameter
values for location (mvar), scale (svar) and shape (gamma and delta).  The
distributions (^dist()^) are all transformations of the Normal (Gaussian)
distribution.


Options
-------

^centiles()^ is the list of estimated centiles (e.g. 50 for the median) to be
    calculated.  Values in cent_list must be separated by commas and/or spaces.

^dist()^ determines the distributional model (see help @xriml@ and Remarks below
    for further details).  If ^dist()^ is not specified, it is taken from the
    macro ^$S_dist^.

^gamma(^#|gvar^)^ defines the (first) shape parameter as a variable (gvar) or as
    a number (#).  If ^gamma()^ is not specified, it is taken from the macro
    ^$S_gamma^.

^delta(^#|dvar^)^ defines the second shape parameter as a variable (dvar) or as
    a number (#).  If ^delta()^ is not specified, it is taken from the macro
    ^$S_delta^.

^cv^ is an option relating to the parameterisation of the S curve for the
    chosen distribution.  See help @xriml@ for more information.

^prefix()^ is the prefix of the names of new variables created to hold the
    estimated centiles, each labelled appropriately.  Default is ^C^.


Remarks
-------

Further details of the distributions:

-------------------------------------------------------------------------------
Code     Name of distribution   Location param.  Scale param.    Shape param(s)
-------------------------------------------------------------------------------
^n^        Normal (Gaussian)      mean             std. dev.       (not applic.)
^en^       Exponential-Normal     median           std. dev.-like  skewness-like
^men^      Modulus exp-Normal     median           std. dev.-like  (see below)
^pn^       Power-Normal           median           std. dev.-like  power transf.
^mpn^      Modulus pow-Normal     median           std. dev.-like  (see below)
^sl^       Shifted lognormal      median           std. dev.-like  skewness-like
-------------------------------------------------------------------------------

The ^mpn^ and ^men^ distributions each have two shape parameters, the first
(denoted by G) related to skewness and the second (denoted by D) related to
kurtosis.


Examples
--------

 . ^centcalc M_ml S_ml, dist(n) centiles(10 90)^
 . ^centcalc M_ml S_ml, dist(en) centiles(10 90) gamma(G_ml)^
 . ^centcalc median cv, dist(pn) centiles(3 25 75 97) gamma(lambda) cv^
 . ^centcalc M S, dist(men) centiles(1 3 50 97 99) gamma(g) delta(d)^


Authors
-------

        Eileen Wright
        Royal Postgraduate Medical School, UK
        ewright@@rpms.ac.uk

        Patrick Royston
        Royal Postgraduate Medical School, UK
        proyston@@rpms.ac.uk


Also see
--------

    STB:  sbe13 (STB-34)
On-line:  help for @xriml@ (if installed)