{smcl} {* 6may2004}{...} {hline} help for {hi:circcentre} {hline} {title:Centring circular data} {p 8 17 2} {cmd:circcentre} {it:varname} [{cmd:if} {it:exp}] [{cmd:in} {it:range}] {cmd:,} {cmdab:g:enerate(}{it:newvar}{cmd:)} [{cmdab:c:entre(}{it:centre}{cmd:)} {cmd:sine} ] {title:Description} {p 4 4 2}{cmd:circcentre} takes {it:varname}, a circular variable between 0 and 360 degrees, and produces a new variable {it:newvar} centring {it:varname} on the direction(s) given by {cmd:centre()}. If {cmd:centre()} is not specified, {cmd:circcentre} looks for a vector mean left behind by {help circsummarize} as {cmd:r(vecmean)}. {it:newvar} varies from -180 degrees to 180 degrees, with centre at 0 degrees. {title:Options} {p 4 8 2}{cmd:generate()} specifies the name of the new variable and is not optional. {p 4 8 2}{cmd:centre()} specifies the direction(s) which correspond to the centre(s) of {it:newvar}. Possibilities are various constants or the name of a variable containing one or more directions. {p 4 8 2}{cmd:sine} specifies that the new variable be expressed on a sine scale, precisely as sine of ({it:varname} - centre) / 2. This transformation pulls in the tails and pushes out the middle of the distribution. For examples of this transformation, see Fisher (1993). {title:Examples} {p 4 8 2}{cmd:. circsummarize wallasp}{p_end} {p 4 8 2}{cmd:. circcentre wallasp, gen(wallasp2)}{p_end} {p 4 8 2}{cmd:. circcentre wallasp, gen(wallasp3) centre(45)} {p 4 8 2}{cmd:. circcentre orient, gen(relflow) centre(iceflow)} {title:Author} {p 4 4 2}Nicholas J. Cox, University of Durham, U.K.{break} n.j.cox@durham.ac.uk {title:References} {p 4 8 2}Fisher, N.I. 1993. {it:Statistical analysis of circular data.} Cambridge: Cambridge University Press. {title:Also see} {p 4 13 2} On-line: help for {help circdiff}, {help circsummarize}