在ggplot2中添加一条水平线来绘制图例和图例 [英] Add a horizontal line to plot and legend in ggplot2

问题描述

这段代码创建了一个漂亮的情节，但是我想在y = 50处添加一条水平黑线，并且图例在图例中显示了带有文本cutoff的黑线，​​但是在图例中留下了点。我可以使用geom_line添加该行，但无法获取图例中的行。

  library（ggplot2）
 the.data<  -  read.table（header = TRUE，sep =， ，
 text =来源，年份，价值
 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（color = so urce））+ 
 geom_smooth（aes（group = 1））
  

解决方案< （1）试试这个：

  cutoff<  -  data.frame（x = c（-Inf ，Inf），y = 50，cutoff = factor（50））
 ggplot（the数据，aes（year，value））+ 
 geom_point（aes（color = source））+ 
 geom_smooth（aes（group = 1））+ 
 geom_line（aes（x，y，linetype = cutoff），cutoff）
  

（2）关于您的评论，如果您不想将截止日期作为单独的传说列出，只需在曲线上标注截止线就会更容易：

<$ （aes（color = source））+
geom_smooth（aes（group = 1））pre> ggplot（the.data，aes（year，value））+
geom_point ）+
geom_hline（yintercept = 50）+
annotate（text，min（the.data $ year），50，vjust = -1，label =Cutoff）


This code creates a nice plot but I would like to add a horizontal black line at y=50 AND have the legend show a black line with the text "cutoff" in the legend, but leave points in the legend for the sources. I can add the line with geom_line but cannot get the line in the legend.

    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))

解决方案

(1) Try this:

cutoff <- data.frame( x = c(-Inf, Inf), y = 50, cutoff = factor(50) )
ggplot(the.data, aes( year, value ) ) + 
        geom_point(aes( colour = source )) + 
        geom_smooth(aes( group = 1 )) + 
        geom_line(aes( x, y, linetype = cutoff ), cutoff)

(2) Regarding your comment, if you don't want the cutoff listed as a separate legend it would be easier to just label the cutoff line right on the plot:

ggplot(the.data, aes( year, value ) ) + 
    geom_point(aes( colour = source )) + 
    geom_smooth(aes( group = 1 )) + 
    geom_hline(yintercept = 50) + 
    annotate("text", min(the.data$year), 50, vjust = -1, label = "Cutoff")

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