R help - Jan 2008 - Range of circular data

I want to get the minimum arc (in degrees) needed to include a set of
compass directions.  I would like to use the range.circular() function
of the package circular, because that package understands a compass-type
of angle convention, but it gives results I don't understand.  Howver, I
can get the correct answer in the example below, 90 degrees, using the
CircStats package.  How can I make the circular package work for me?
> R.version.string
[1] "R version 2.6.1 (2007-11-26)"
> library(circular)
> y <- circular(c(45, 135), units = "degrees", template =
"geographics")
> range.circular(y)
Circular Data:
Type = angles
Units = degrees
Template = geographics
Modulo = asis
Zero = 1.570796
Rotation = clock
[1] 0

Just in case range.circular() expects radians, I tried this:
> range.circular(rad(y))
Circular Data:
Type = angles
Units = degrees
Template = geographics
Modulo = asis
Zero = 1.570796
Rotation = clock
[1] 88.4292

I can get the correct answer using CircStats instead:
> library(CircStats)
> y <- rad(c(45, 135))
> 180*circ.range(y)/pi
  range
1    90

Thanks,
Scott Waichler
Pacific Northwest National Laboratory
scott.waichler _at_ pnl.gov

> I want to get the minimum arc (in degrees) needed to include a set of
> compass directions.  I would like to use the range.circular() function
> of the package circular, because that package understands a compass-type
> of angle convention, but it gives results I don't understand.  Howver,
I
> can get the correct answer in the example below, 90 degrees, using the
> CircStats package.  How can I make the circular package work for me?
> 
> > R.version.string
> [1] "R version 2.6.1 (2007-11-26)"
> 
> > library(circular)
> > y <- circular(c(45, 135), units = "degrees", template =
"geographics")
> > range.circular(y)
> Circular Data:
> Type = angles
> Units = degrees
> Template = geographics
> Modulo = asis
> Zero = 1.570796
> Rotation = clock
> [1] 0
Using y <- circular(c(45, 135), units = "degrees");
range.circular(y)
gives the correct answer.
Circular Data: 
Type = angles 
Units = degrees 
Template = none 
Modulo = asis 
Zero = 0 
Rotation = counter 
[1] 90

The different answers are generated in the subfunction conversion.circular 
- take a look in there to see what is going on.

Regards,
Richie.

Mathematical Sciences Unit
HSL


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