更改折线图特征以通知这些值是预测值

Question

假设我有以下数据，并希望使用ggplot2绘制折线图。数据包括五天的数据，星期四和星期五是预测。我怎样才能创建一些方案来从星期四到星期五（或不同的颜色背景）划线，以便我有一种直观的方式来表示这些值是预测。

示例数据：

df = data.frame(date=c("mon","tues","wed","thurs","fri"),
                gals=c(4,6,2,5,3),
                cups=c(30,25,27,22,25))
df
library(reshape)
d = melt(df, id="date")
d
ggplot(d, aes(date, value, group=variable, colour=variable)) + geom_line(lwd=1.15) 

Answer 1

你必须像这样绘制2条线，并为每条线分组数据。请记住向“已知”系列添加一个点，以便它与“未知”数据结合：

require(reshape)
df = data.frame(date=c("mon","tues","wed","thurs","fri"),
            gals=c(4,6,2,5,3),
            cups=c(30,25,27,22,25))

d = melt(df, id="date")
# select the points you know + 1 to join up the line
known<-d[which(d$date %in% c("mon","tues","wed","thurs")),]
# select the points you don't know
unknown<-d[which(d$date %in% c("thurs","fri")),]

ggplot() + 
   geom_line(data=known, aes(x=date, y=value, group=variable, colour=variable)) + 
# use linetype=2 for a dotted line
geom_line(data=unknown, aes(x=date, y=value, group=variable, colour=variable), linetype=2) + 
 # this is to make the days display in order
scale_x_discrete(limits=c("mon","tues","wed","thurs","fri"))