{smcl}
{* 22dec2003}{...}
{hline}
help for {hi:circrplot}
{hline}

{title:Raw data plot for circular data with spikes}

{p 8 17 2}
{cmd:circrplot}
{it:varname}
[{cmd:if} {it:exp}] 
[{cmd:in} {it:range}]
[{cmd:,}
{cmdab:cla:bel(}{it:label_specification}{cmd:)} 
{cmdab:ctic:k(}{it:numlist}{cmd:)} 
{cmdab:result:ant(}{it:resultant_options}{cmd:)} 
{cmd:round(}{it:#}{cmd:)} 
{cmdab:tick:length(}{it:#}{cmd:)}
{it:twoway_options} 
] 


{title:Description} 

{p 4 4 2} 
{cmd:circrplot} produces a raw data plot for {it:varname} with spikes showing
frequencies. {it:varname} should be a circular variable taking on values
between 0 and 360 degrees.

{p 4 4 2} 
Strictly, the values of {it:varname} are rounded to the nearest degree, or to
the argument of {cmd:round()}. Spikes are drawn outwards from the circumference
of a circle pointing in each direction present in the data. The length of each
spike 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. 

{p 4 4 2} 
The graph will usually best be shown with {cmd:xsize()} and {cmd:ysize()}
equal, or nearly so. It may be helpful to know that the centre of the circle is
at {it:x} = 0, {it: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. 


{title:Options} 

{p 4 8 2} 
{cmd: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 {cmd:" "} following each label. For example, 
the default is {cmd:clabel(0 "N" 90 "E" 180 "S" 270 "W")}.

{p 4 8 2} 
{cmd:ctick()} specifies positions of ticks to be shown inside the circle
at angles measured clockwise from 0 (North) through 360 degrees. 

{p 4 8 2}{cmd:resultant()} specifies options controlling the rendering of the
arrow showing the resultant. In particular, {cmd:arrowheadlength()} specifies
the arrowhead length (default 0.1).  Otherwise, such options are typically
appropriate {help connect_options}. 

{p 4 8 2}
{cmd:round()} indicates the bin or class width to be used (default 1 deg).

{p 4 8 2} 
{cmd:ticklength()} specifies the tick length (default 0.05). 

{p 4 8 2} 
{it:twoway_options} are options of {help twoway_options:twoway}.  
By default the {cmd:subtitle()} indicates the mean direction and vector 
strength and is at {cmd:pos(6)}.  Note that the degree symbol can be specified 
by {cmd:`=char(176)'}. 


{title:Example} 

{p 4 8 2}{cmd:. circrplot wallasp, text(-0.5 0 "Wall aspect", size(large))}{p_end}
{p 4 8 2}{cmd:. graph display, xsize(4) ysize(4)} 


{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 circdplot} (if installed),  
{help circvplot} (if installed) 

