Adding seperate features to facet plots

[Brian Weaver]

Hello All,

I am trying to add horizontal lines to plots that have been faceted (if that is  a word).  However, the different plots have their data centered around two different means, one being 1000 and the other being 4000.  My goal is to be able to add a horizontal line at 1000 to the plot where the data is centered around 1000 only and also a horizontal line at 4000 for the other plot only.  The following code may help get the idea across of what I want.  Both of the plots created by the facet have a horizontal line at 1000 when I only want the bottom one to and then likewise add a horizontal line at 4000 for the top plot.  Thank you in advance.

Brian

y.l <- rnorm(50,mean = 1000, sd = 0.001)
y.u <- rnorm(50,mean = 4000, sd = 0.001)

dat <- data.frame(Observe = round(c(y.l,y.u),digits = 3),Time = rep(1:50,2),Standard = c(rep("Low",50),rep("High",50)) )

qplot(Time,Observe,data = dat, geom = c("point","path")) + facet_grid(Standard~., scale = "free") + geom_smooth() +
geom_hline(aes(yintercept = 1000))

[ONKELINX, Thierry]

Dear Brian,

Here are two solutions. Note that you can create the same dummy dataset
with much less code ;-)

Best regards,

Thierry

library(ggplot2)

#Solution 1: add the reference level to the entire dataset
dat <- expand.grid(Time = 1:50, Mean = c(1000, 4000))
dat$Observe <- round(rnorm(nrow(dat), mean = dat$Mean, sd = 0.01),
digits = 3)
dat$Standard <- factor(dat$Mean, labels = c("Low", "High"))

ggplot(dat, aes(x = Time, y = Observe)) + geom_hline(aes(yintercept =
Mean)) + geom_smooth() + geom_point() + geom_path() + facet_wrap(~
Standard, scales = "free", ncol = 1)

#solution 2: create an extra dataset with the reference level per
standard
Reference <- unique(dat[, c("Mean", "Standard")])
dat$Mean <- NULL
ggplot(dat, aes(x = Time, y = Observe)) + geom_hline(data = Reference,
aes(yintercept = Mean)) + geom_smooth() + geom_point() + geom_path() +
facet_wrap(~ Standard, scales = "free", ncol = 1)

------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium

Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium

tel. + 32 54/436 185
Thierry....@inbo.be
www.inbo.be

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ensure that a reasonable answer can be extracted from a given body of
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