In the most recent version of ggplot2, ?fortify returns:
Description
Rather than using this function, I now recomend using the broom package, which implements a much wider range of methods.
fortifymay be deprecated in the future.
The broom package indeed offers many alternatives (such as augment). Which one should be used in what circumstances?
I am particularly interested in an alternative to fortify(spdf) where spdf is a SpatialPolygonsDataFrame.
Answer
Here's how I approached the subject.
After searching "broom cran" I was redirected to the corresponding page of the package on CRAN. It offers a few vignettes so I checked out Introduction to broom. After failing to find any string matching "spatial" I closed the PDF and opened the reference manual. Searching for "spatial" I got 7 hits, with the first one on the topic of sp_tidiers. Function tidy is advertised to convert a spatial object to a data.frame. Let's try it.
library(sp)
Sr1 = Polygon(cbind(c(2,4,4,1,2),c(2,3,5,4,2)))
Sr2 = Polygon(cbind(c(5,4,2,5),c(2,3,2,2)))
Sr3 = Polygon(cbind(c(4,4,5,10,4),c(5,3,2,5,5)))
Sr4 = Polygon(cbind(c(5,6,6,5,5),c(4,4,3,3,4)), hole = TRUE)
Srs1 = Polygons(list(Sr1), "s1")
Srs2 = Polygons(list(Sr2), "s2")
Srs3 = Polygons(list(Sr3, Sr4), "s3/4")
x = SpatialPolygons(list(Srs1,Srs2,Srs3), 1:3)
library(broom)
tidy(x)
long lat order hole piece group id
1 2 2 1 FALSE 1 s1.1 s1
2 1 4 2 FALSE 1 s1.1 s1
3 4 5 3 FALSE 1 s1.1 s1
4 4 3 4 FALSE 1 s1.1 s1
5 2 2 5 FALSE 1 s1.1 s1
6 5 2 1 FALSE 1 s2.1 s2
7 2 2 2 FALSE 1 s2.1 s2
8 4 3 3 FALSE 1 s2.1 s2
9 5 2 4 FALSE 1 s2.1 s2
10 4 5 1 FALSE 1 s3/4.1 s3/4
11 10 5 2 FALSE 1 s3/4.1 s3/4
12 5 2 3 FALSE 1 s3/4.1 s3/4
13 4 3 4 FALSE 1 s3/4.1 s3/4
14 4 5 5 FALSE 1 s3/4.1 s3/4
15 5 4 6 TRUE 2 s3/4.2 s3/4
16 5 3 7 TRUE 2 s3/4.2 s3/4
17 6 3 8 TRUE 2 s3/4.2 s3/4
18 6 4 9 TRUE 2 s3/4.2 s3/4
19 5 4 10 TRUE 2 s3/4.2 s3/4