I am trying to replicate Hadley Wickham's example on page 86 of the ggplot2 book, where he overlays geom_rects showing the party in power over the trend in unemployment. Here is my core code, with some sample data:
library("ggplot2")
library("reshape2")
library("lubridate")
con <- textConnection("Date,Var1,Var2
8-Jan-12,100.8,116
15-Jan-12,99.4,115.5
22-Jan-12,98.4,115
28-Jan-12,97.1,114
4-Feb-12,95.9,112
11-Feb-12,95.3,113
18-Feb-12,93.9,111.5
25-Feb-12,93.5,111.5
3-Mar-12,92.6,110
10-Mar-12,91.4,108
17-Mar-12,90.2,106.8
24-Mar-12,90,107.5
31-Mar-12,89.9,106
5-Apr-12,90.4,106.5
12-Apr-12,89.8,106")
track <- read.csv(con, header=TRUE)
track$Date <- as.Date( dmy(track$Date) )
track <- melt(track,
id.vars = c("Date"))
con <- textConnection("City,From,To
Auckland,5-Apr-12,10-Apr-12
Brussels,1-Apr-12,3-Apr-12
Cleveland,24-Jan-12,26-Jan-12
Darjeeling,18-Jan-12,19-Jan-12
Erehwon,8-Feb-12,10-Feb-12
Florence,5-Mar-12,7-Mar-12
Gandalf,25-Mar-12,27-Mar-12")
trips <- read.csv(con, header=TRUE)
trips$From <- as.Date( dmy(trips$From) )
trips$To <- as.Date( dmy(trips$To) )
# draw the Time Series data
p <- ggplot(track,
aes(x = Date,
y = value,
colour=variable,
group = variable))
p <- p + geom_smooth()
p <- p + geom_point(size=3)
p <- p + geom_vline(data=trips,
aes(xintercept=From),
colour='steelblue') # departure dates
p <- p + geom_vline(data=trips,
aes(xintercept=To),
colour='grey80') # return dates
yrng <- c(80,120)
p <- p + scale_y_continuous(limits=yrng)
p # this works up to here, using vlines (ugly, but makes the point)
# ----------- THIS geom_rect() STOPS THIS PLOT BEING RENDERED
p2 <- p + geom_rect(aes(NULL, NULL, xmin=From, xmax=To),
ymin=yrng[1], ymax=yrng[2],
data=trips)
p2 # this gives an error message
# Error in eval(expr, envir, enclos) : object 'variable' not found
# ----------- THIS NOW WORKS, THANKS TO @smu, SEE BELOW
p2 <- p + geom_rect(aes(NULL, NULL, xmin=From, xmax=To,
colour=NULL, group=NULL),
ymin=yrng[1], ymax=yrng[2],
fill='orange',
alpha=0.4,
data=trips)
p2 # and I have added fill and alpha to prettify it a bit
As suggested by @tyler-rinker, I have edited the code to include the original error and the solution pointed out by @smu. Thanks.
Just adding inherit.aes=FALSE
in your geom_rect
actually works better as it won't change any of the settings you had made to your previous graph (legend etc.)
In the first ggplot
call you map the colour
to 'variable'. This mapping is still present in the geom_rect
call, but no variable named 'variable' exists in 'trips'. I would suggest to unmap colour using:
p2 <- p + geom_rect(aes(NULL, NULL, xmin=From, xmax=To, colour=NULL),
ymin=yrng[1], ymax=yrng[2],
data=trips)
(Haven't tried it, but I guess it should work).
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