{smcl} {* 22feb2008}{...} {cmd:help centcalc}{right:Patrick Royston} {hline} {title:Centile calculation} {title:Syntax} {p 8 12 2} {cmd:centcalc} {it:mvar} {it:svar} [{cmd:,} {it:options} ] {synoptset 20 tabbed}{...} {synopthdr} {synoptline} {synopt :{opt c:entiles(numlist)}}defines the required centiles of {it:yvar}|{it:xvar}{p_end} {synopt :{opt di:st(dist_name)}}specifies the distribution of the response variable{p_end} {synopt :{opt g:amma(# | gvar)}}G{p_end} {synopt :{opt de:lta(# | dvar)}}D{p_end} {synopt :{opt cv}}produces estimated parameters and centiles at all non-missing values of {it:xvar}{p_end} {synopt :{opt p:refix(stub)}}defines a censoring variable{p_end} {synoptline} {p2colreset}{...} {title:Description} {pstd} {opt centcalc} calculates distribution-based centiles from user-supplied parameter values for location ({it:mvar}), scale ({it:svar}) and shape ({opt gamma()} and {opt delta()}). The distributions ({opt dist()}) are all transformations of the Normal (Gaussian) distribution. {title:Options} {phang} {opt centiles(numlist)} is the list of estimated centiles (e.g. 50 for the median) to be calculated. {phang} {opt cv} is an option relating to the parameterisation of the S-curve for the chosen distribution. See {help xriml} for more information. {phang} {opt delta(# | dvar)} defines the (second) shape parameter as a variable ({it:dvar}) or as a number ({it:#}). If {opt delta()} is not specified, it is taken from the macro {opt \$S_delta}. {phang} {opt dist(dist_name)} determines the distributional model (see {help xriml} and Remarks below for further details). {it:dist_name} must be one of {opt n}, {opt en}, {opt men}, {opt pn}, {opt mpn}, or {opt sl}. If {opt dist()} is not specified, {it:dist_name} is taken from the macro {opt \$S_dist}. {phang} {opt gamma(# | gvar)} defines the (first) shape parameter as a variable ({it:gvar}) or as a number ({it:#}). If {opt gamma()} is not specified, it is taken from the macro {opt \$S_gamma}. {phang} {opt prefix(stub)} is the prefix of the names of new variables created to hold the estimated centiles, each labelled appropriately. Default {it:stub} is {opt C}. {title:Remarks} {pstd} Further details of the distributions: -------------------------------------------------------------------------- Code Name of distribution Location Scale Shape param(s) -------------------------------------------------------------------------- {opt n} Normal (Gaussian) mean std. dev. (not applic.) {opt en} Exponential-Normal median std. dev.-like skewness-like {opt men} Modulus exp-Normal median std. dev.-like (see below) {opt pn} Power-Normal median std. dev.-like power transf. {opt mpn} Modulus pow-Normal median std. dev.-like (see below) {opt sl} Shifted lognormal median std. dev.-like skewness-like -------------------------------------------------------------------------- {pstd} The {opt mpn} and {opt men} distributions each have two shape parameters, the first (denoted by G) related to skewness and the second (denoted by D) related to kurtosis. {title:Examples} {phang} {cmd:. centcalc M_ml S_ml, dist(n) centiles(10 90)} {phang} {cmd:. centcalc M_ml S_ml, dist(en) centiles(10 90) gamma(G_ml)} {phang} {cmd:. centcalc median cv, dist(pn) centiles(3 25 75 97) gamma(lambda) cv} {phang} {cmd:. centcalc M S, dist(men) centiles(1 3 50 97 99) gamma(g) delta(d)} {title:Author} {pstd} Patrick Royston, MRC Clinical Trials Unit, London. patrick.royston@ctu.mrc.ac.uk {pstd} Eileen Wright, Macclesfield {title:Also see} {psee} Manual: {bf:[R] fracpoly} {psee} Online: {help xriml}, {help xrigls} (if installed), {help fracpoly} {p_end}