このコードは素敵なプロットを作成しますが、y = 50 に水平の黒い線を追加し、凡例に「カットオフ」というテキストを含む黒い線を凡例に表示させたいのですが、ソースの凡例にポイントを残します。geom_line で行を追加できますが、凡例で行を取得できません。
library(ggplot2)
the.data <- read.table( header=TRUE, sep=",",
text="source,year,value
S1,1976,56.98
S1,1977,55.26
S1,1978,68.83
S1,1979,59.70
S1,1980,57.58
S1,1981,61.54
S1,1982,48.65
S1,1983,53.45
S1,1984,45.95
S1,1985,51.95
S1,1986,51.85
S1,1987,54.55
S1,1988,51.61
S1,1989,52.24
S1,1990,49.28
S1,1991,57.33
S1,1992,51.28
S1,1993,55.07
S1,1994,50.88
S2,1993,54.90
S2,1994,51.20
S2,1995,52.10
S2,1996,51.40
S3,2002,57.95
S3,2003,47.95
S3,2004,48.15
S3,2005,37.80
S3,2006,56.96
S3,2007,48.91
S3,2008,44.00
S3,2009,45.35
S3,2010,49.40
S3,2011,51.19")
ggplot(the.data, aes( x = year, y = value ) ) +
geom_point(aes(colour = source)) +
geom_smooth(aes(group = 1))