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Graph effects of individual circular values on vector mean and vector strength

circovmeanvarname[ifexp] [inrange] [,nolistcircscatter_options]

circovstrvarname[ifexp] [inrange] [,nolistcircscatter_options]

Description

circovmeanandcircovstrlist and graph the effects of omitting individual values on the vector mean and vector strength respectively of a circular variable measured on a scale between 0 and 360 degrees. For more information on these measures, see circsummarize.

RemarksShowing the effects of omitting individual circular values on summary measures is a simple way of screening for outliers and/or assessing the importance of apparent or obvious outliers. Barnett and Lewis (1994, Ch.11) supply more discussion and references on working with possible circular outliers. One of their examples concerns homing directions, measured as degrees from North) of 14 northern cricket frogs

Acriscrepitans(Ferguson, Landreth and McKeown 1967; Collett 1980): 104, 110, 117, 121, 127, 130, 136, 145, 152, 178, 184, 192, 200, 316.

Options

nolistsuppresses the listing of values.

circscatter_optionsare options of circscatter.

Examples

. circovmean axisasp

AuthorNicholas J. Cox, University of Durham, U.K. n.j.cox@durham.ac.uk

ReferencesBarnett, V. and Lewis, T. 1994.

Outliers in statistical data.Chichester: John Wiley. (Previous editions: 1978, 1984.)Collett, D. 1980. Outliers in circular data.

Applied Statistics29: 50--57.Ferguson, D.E., Landreth, H.F. and McKeown, J.P. 1967. Sun compass orientation of the northern cricket frog,

Acris crepitans.AnimalBehaviour15: 45--53.

Also seeOn-line: help for circsummarize, circmedian, circscatter