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Identifying peak periods of observations in circular yearly data

5 messages · Jim Lemon, Daisy Englert Duursma, David L Carlson

Original
Daisy Englert Duursma
# 
Greetings,

I am trying to identify at which point during the year 80% of bird breeding
observations are. typically I would answer a question like this by finding
the median or quartiles but how do I deal with situations where the 80% of
the is from day 285 through day 366 (leap year) and extends to day 30?

The data is circular and and day 365 is as close to day 366 as day 1.

I am reading the manual for CircStats and circular but I could really use
some help on this.


Here is some dummy data:


obsDay<-c(rep(1:30,10),rep(45:65,2),65:180,rep(181:265,2),rep(266:330,4),rep(331:366,6))

plot(density(obsDay))
Jim Lemon
# 
Hi Daisy,
You face a problem similar to one with which I have grappled in
different fields. The year is designed for the northern hemisphere,
beginning and ending in less productive biologic states in those
regions. I have previously argued that since the calendar year is an
arbitrary progression, it makes more sense to redraw the annual
boundary when examining things like this in the southern hemisphere.
That is to say, a "year" is conventionally marked at about the
northern winter solstice. Down here, this becomes the summer solstice
and breaks up a lot of things that happen around that time. Have you
thought of defining a southern bird-watching year as beginning and
ending at the southern winter solstice? As I am currently writing in
an entirely different context, it shouldn't really make much
difference.

Jim


On Wed, May 27, 2015 at 4:35 PM, Daisy Englert Duursma
<daisy.duursma at gmail.com> wrote:
Daisy Englert Duursma
# 
Thanks for the advice Jim. I did actually play around with this idea, but
for some bird species (emu) the beginning of the breeding season is
actually January while for others it is in July or at other times. Breeding
seasons can be driven by dry season or temperatures, so although there are
generalizations each species need to be assessed.
On Wed, May 27, 2015 at 7:34 PM, Jim Lemon <drjimlemon at gmail.com> wrote:

            

      
      
      
    

        

      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      David L Carlson
    

    

      
      #
    

  


  

      
You can use package circular for this. You have to convert 1-366 to 1-360 by dividing the days by 366 and multiplying by 360 and converting the results back to days by adding 360 if the value is <0 and dividing by 360 and multiplying by 366:

            

      
      
      
    

        
Circular Data: 
Type = angles 
Units = degrees 
Template = geographics 
Modulo = asis 
Zero = 1.570796 
Rotation = clock 
[1] -23.5503

            

      
      
      
    

        
Circular Data: 
Type = angles 
Units = degrees 
Template = geographics 
Modulo = asis 
Zero = 1.570796 
Rotation = clock 
[1] -17.70492
attr(,"medians")
[1] 342.2951

            

      
      
      
    

        
[1] 1.28903

            

      
      
      
    

        
Circular Data: 
Type = angles 
Units = degrees 
Template = geographics 
Modulo = asis 
Zero = 1.570796 
Rotation = clock 
       10%        90% 
  59.01639 -135.73770

            

      
      
      
    

        
10% 90% 
 60 228

            

      
      
      
    

        
+     template="geographics", zero=0, tcl.text=.15)

            

      
      
      
    

        
-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Daisy Englert Duursma
Sent: Wednesday, May 27, 2015 4:42 AM
To: Jim Lemon
Cc: r-help at R-project.org
Subject: Re: [R] Identifying peak periods of observations in circular yearly data

Thanks for the advice Jim. I did actually play around with this idea, but
for some bird species (emu) the beginning of the breeding season is
actually January while for others it is in July or at other times. Breeding
seasons can be driven by dry season or temperatures, so although there are
generalizations each species need to be assessed.

        
On Wed, May 27, 2015 at 7:34 PM, Jim Lemon <drjimlemon at gmail.com> wrote:

        

            

      
      
      
    

        

      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Jim Lemon
    

    

      
      #
    

  


  

      
Hi Daisy,
Let me rephrase what I said. Are you looking for 80% of bird breeding
observations for a given species in a calendar year (I think not), or
in the breeding season for that species, which may not be strongly
linked to a calendar year? Your example data, when plotted like this:

hist(obsDay,breaks=seq(0,380,by=20))

look like breeding begins at about the middle of the year, increases
in intensity until the first month or two in the next year and then
declines sharply until the middle of that year. Getting the 80% in a
calendar year is easy, but I don't think it means anything in terms of
breeding behavior. My comment, which probably was pretty obscure, was
that I think you are looking for the beginning of the breeding season
in order to calculate the quantile or if you want to predict when that
quantile will occur, then go looking for the kernel density of the
observed historical distribution.

Jim

        
On Thu, May 28, 2015 at 2:02 AM, David L Carlson <dcarlson at tamu.edu> wrote: