{smcl} {* 3may2004}{...} {hline} help for {hi:circvm} {hline} {title:Fit von Mises distribution to circular data} {p 8 17 2} {cmd:circvm} {it:varlist} [{cmd:if} {it:exp}] [{cmd:in} {it:range}] {p 8 17 2} {cmd:circvm} {it:varname} [{cmd:if} {it:exp}] [{cmd:in} {it:range}] [{cmd:, by(}{it:byvar}{cmd:)}] {title:Description} {p 4 4 2} {cmd:circvm} fits von Mises (a.k.a. circular normal) distributions to circular variables in {it:varlist} with scales between 0 and 360 degrees. With a single {it:varname} and a {cmd:by()} option, distributions are fitted separately for groups defined by the distinct values of {it:byvar}. {p 4 4 2}The parameters fitted are the vector mean and the concentration parameter kappa, calculated from the vector strength {it:R} by 2 * {it:R} + {it:R}^3 + 5 * {it:R}^5 / 6, {it:R} < 0.53; -0.4 + 1.39 * {it:R} + 0.43 / (1 - {it:R}), {it:R} < 0.85; 1 / ({it:R}^3 - 4 * {it:R}^2 + 3 * {it:R}), {it:R} >= 0.85. {p 4 4 2}See Fisher (1993) for details and discussion. {title:Options} {p 4 8 2} {cmd:by()} indicating grouping is allowed with a single {it:varname}. {title:Examples} {p 4 4 2}{cmd:. circvm wallasp axisasp}{p_end} {p 4 4 2}{cmd:. circvm wallasp, by(grade)} {title:References} {p 4 8 2} Fisher, N.I. 1993. {it:Statistical analysis of circular data.} Cambridge: Cambridge University Press. {title:Author} {p 4 4 2}Nicholas J. Cox, University of Durham, U.K.{break} n.j.cox@durham.ac.uk {title:Also see} {p 4 13 2} On-line: help for {help circqvm}, {help circpvm}