[R-sig-Geo] Changing coords in SpatialPolgyon

[Nick Matzke]

Hi -- I am trying to change the coordinates of the points in 
a polygon (after shrinking the polygon towards the centroid.

However, any way I try it (direct assignment, slot(), 
attr()), I get this error:

=================
object of type 'S4' is not subsettable
=================


Here's an example of the error, showing the objects I'm 
using.  Any help **much** appreciated.

===========================


 > 				class(all_emerged_islands_at_this_height_break)
[1] "SpatialPolygons"
attr(,"package")
[1] "sp"
 > 				all_emerged_islands_at_this_height_break
An object of class "SpatialPolygons"
Slot "polygons":
[[1]]
An object of class "Polygons"
Slot "Polygons":
[[1]]
An object of class "Polygon"
Slot "labpt":
[1] 91.44457 25.55424

Slot "area":
[1] 0.25305

Slot "hole":
[1] FALSE

Slot "ringDir":
[1] 1

Slot "coords":
            x      y
  [1,] 91.273 25.804
  [2,] 91.348 25.817
  [3,] 91.408 25.844
  [4,] 91.498 25.831
  [5,] 91.528 25.763
  [6,] 91.573 25.694
  [7,] 91.633 25.681
  [8,] 91.723 25.681
  [9,] 91.768 25.626
[10,] 91.768 25.544
[11,] 91.768 25.448
[12,] 91.708 25.380
[13,] 91.648 25.312
[14,] 91.558 25.298
[15,] 91.468 25.298
[16,] 91.378 25.325
[17,] 91.318 25.380
[18,] 91.228 25.421
[19,] 91.123 25.435
[20,] 91.108 25.558
[21,] 91.123 25.640
[22,] 91.198 25.708
[23,] 91.258 25.776
[24,] 91.273 25.804



Slot "plotOrder":
[1] 1

Slot "labpt":
[1] 91.44457 25.55424

Slot "ID":
[1] "89"

Slot "area":
[1] 0.25305


[[2]]
An object of class "Polygons"
Slot "Polygons":
[[1]]
An object of class "Polygon"
Slot "labpt":
[1] 92.00535 25.12364

[...etc...]


 > 				
 > 				class(tmppoly_shrunken)
[1] "Polygon"
attr(,"package")
[1] "sp"
 > 				tmppoly_shrunken
An object of class "Polygon"
Slot "labpt":
[1] 91.44457 25.55424

Slot "area":
[1] 25.29848

Slot "hole":
[1] FALSE

Slot "ringDir":
[1] 1

Slot "coords":
              x        y
  [1,] 89.72883  3.00000
  [2,] 90.47883 28.18185
  [3,] 91.07883 28.45185
  [4,] 91.97883 28.32185
  [5,] 92.27883 27.64185
  [6,] 92.72883 26.95185
  [7,] 93.32883 26.82185
  [8,] 94.22883 26.82185
  [9,] 94.67883 26.27185
[10,] 94.67883 25.45185
[11,] 94.67883 24.49185
[12,] 94.07883 23.81185
[13,] 93.47883 23.13185
[14,] 92.57883 22.99185
[15,] 91.67883 22.99185
[16,] 90.77883 23.26185
[17,] 90.17883 23.81185
[18,] 89.27883 24.22185
[19,] 88.22883 24.36185
[20,] 88.07883 25.59185
[21,] 88.22883 26.41185
[22,] 88.97883 27.09185
[23,] 89.57883 27.77185
[24,] 89.72883 28.05185

 > 				
 > 			 
slot(all_emerged_islands_at_this_height_break[j]@polygons[[1]]@Polygons[[1]], 
"coords", check=FALSE) = slot(tmppoly_shrunken, "coords")
Error in 
slot(all_emerged_islands_at_this_height_break[j]@polygons[[1]]@Polygons[[1]], 
  :
   object of type 'S4' is not subsettable
 >
 >
===========================


-- 
====================================================
Nicholas J. Matzke
Ph.D. Candidate, Graduate Student Researcher

Huelsenbeck Lab
Center for Theoretical Evolutionary Genomics
4151 VLSB (Valley Life Sciences Building)
Department of Integrative Biology
University of California, Berkeley

Graduate Student Instructor, IB200B
Principles of Phylogenetics: Ecology and Evolution
http://ib.berkeley.edu/courses/ib200b/
http://phylo.wikidot.com/


Lab websites:
http://ib.berkeley.edu/people/lab_detail.php?lab=54
http://fisher.berkeley.edu/cteg/hlab.html
Dept. personal page: 
http://ib.berkeley.edu/people/students/person_detail.php?person=370
Lab personal page: 
http://fisher.berkeley.edu/cteg/members/matzke.html
Lab phone: 510-643-6299
Dept. fax: 510-643-6264

Cell phone: 510-301-0179
Email: matzke at berkeley.edu

Mailing address:
Department of Integrative Biology
1005 Valley Life Sciences Building #3140
Berkeley, CA 94720-3140

-----------------------------------------------------
"[W]hen people thought the earth was flat, they were wrong. 
When people thought the earth was spherical, they were 
wrong. But if you think that thinking the earth is spherical 
is just as wrong as thinking the earth is flat, then your 
view is wronger than both of them put together."

Isaac Asimov (1989). "The Relativity of Wrong." The 
Skeptical Inquirer, 14(1), 35-44. Fall 1989.
http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm