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Raw data plot for circular data with point symbols

circdplotvarname[ifexp] [inrange] [,clabel(label_specification)ctick(numlist)fudge(#)resultant(resultant_options)round(#)ticklength(#)unit(#)twoway_options]

Description

circdplotproduces a raw data plot forvarnamewith point symbols showing values.varnameshould be a circular variable taking on values between 0 and 360 degrees.Strictly, the values of

varnameare rounded to the nearest degree, or to the argument ofround(). Rays of point symbols are drawn outwards from the circumference of a circle pointing in each direction present in the data. The length of each ray is proportional to the frequency of that direction. The resultant or mean direction is indicated by an arrow from the centre of the circle with length the radius of the circle X the vector strength. Hence an arrow representing a mean direction with vector strength 1 would touch the circle.The graph will usually best be shown with

xsize()andysize()equal, or nearly so. It may be helpful to know that the centre of the circle is atx= 0,y= 0 and that it has radius 1, so that the cardinal points North, East, South, West are at 0,1; 1,0; 0,-1; -1,0.

Options

clabel()specifies labels to be shown inside the circle at angles measured clockwise from 0 (North) through 360 degrees. Single text labels may be specified within" "following each label. For example, the default isclabel(0 "N" 90 "E" 180 "S" 270 "W").

ctick()specifies positions of ticks to be shown inside the circle at angles measured clockwise from 0 (North) through 360 degrees.

fudge()specifies a fudge factor controlling the radial spacing of point symbols. Default 1 means that the outermost point symbol will be plotted at distance from the circle equal to the radius of that circle. # means maximum distance # X that radius. Most graphs will need some hand-tuning offudge()for better appearance. See alsoround().

resultant()specifies options controlling the rendering of the arrow showing the resultant. In particular,arrowheadlength()specifies the arrowhead length (default 0.1). Otherwise, such options are typically appropriate connect_options.

round()indicates the bin or class width to be used (default 1 deg). See alsofudge().

ticklength()specifies the tick length (default 0.05).

unit()specifies that a point symbol should represent at most#observations, which number should be >= 1. That is,unit(10)specifies that a point symbol should represent at most 10 observations. Strictly, frequencies in each bin will be rounded up to the nearest multiple of#, so that withunit(10)1 to 10 observations would be represented by one point symbol, 11 to 20 two symbols, and so forth.

twoway_optionsare options of twoway. By default thesubtitle()indicates the mean direction and vector strength and is atpos(6). Note that the degree symbol can be specified by`=char(176)'.

Example

. circdplot wallasp, result(clcolor(blue) clw(thick)) round(2)fudge(0.25) ms(Oh) mcolor(red) text(-0.5 0 "Wall aspect",size(large)). graph display, xsize(4) ysize(4)

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

Also seeOn-line: help for circrplot (if installed), circvplot (if installed)