[R] Range of circular data

From: Waichler, Scott R <Scott.Waichler_at_pnl.gov>
Date: Mon, 7 Jan 2008 17:05:17 -0800


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



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