Place title of multiplot panel with ggplot2

Question

From the help found here I've managed to create this multiplot panel: with the following code:

library(zoo)
library(ggplot2)

datos=read.csv("paterna.dat",sep=";",header=T,na.strings="-99.9")

datos$dia=as.POSIXct(datos[,1], format="%y/%m/%d %H:%M:%S")

datos$Precipitación[is.na(datos$Precipitación)]=0
xlim = as.POSIXct(c("2010-05-12 00:00:00", "2010-05-12 23:50:00"))
ylim = trunc(max(datos$Precipitación) + 5)
tmax = trunc(max(datos$Temperatura) + 5)
tmin = trunc(min(datos$Temperatura) - 5)

tmx = max(datos$Temperatura) 
tmxpos=which.max(datos$Temperatura) 
tmn = min(datos$Temperatura) 
tmnpos=which.min(datos$Temperatura) 

tmp=ggplot(data=datos,aes(x=dia, y=Temperatura)) + geom_line(colour="red") + ylab("Temperatura (ºC)") + 
xlab(" ") + scale_x_datetime(limits=xlim ,format = "%H",major='hour') + scale_y_continuous(limits = c(tmin,tmax)) + geom_text(data=datos[tmxpos,], label=tmx, vjust=-1.5, colour="red") + geom_text(data=datos[tmnpos,], label=tmn, vjust=1.5, colour="blue")

pre=ggplot(data=datos,aes(x=dia, y=Precipitación)) + geom_bar(colour="blue",stat="identity",fill="blue") +
ylab("Precipitación (l)") + xlab("Hora solar") + scale_x_datetime(limits=xlim ,format = "%H",major='hour') + scale_y_continuous(limits=c(0,ylim))

vel=ggplot(data=datos,aes(x=dia, y=Velocidad)) + geom_line(colour="brown") + ylab("Velocidad (km/h)") + xlab(" ")  + scale_x_datetime(limits=xlim ,format = "%H",major='hour') + scale_y_continuous(limits = c(0,100))

dir=ggplot(data=datos,aes(x=dia, y=Dirección)) + geom_line(colour="brown") + ylab("Dirección viento (grados)") + xlab(" ") + scale_x_datetime(limits=xlim ,format = "%H",major='hour') + scale_y_continuous(limits = c(0,360))

hum=ggplot(data=datos,aes(x=dia, y=Humedad.Relativa)) + geom_line(colour="blue") + ylab("Humedad relativa (%)") + xlab(" ") + scale_x_datetime(limits=xlim ,format = "%H",major='hour') + scale_y_continuous(limits = c(0,100))

grid.newpage()
pushViewport(viewport(layout = grid.layout(3, 2)))   
print(tmp, vp = viewport(layout.pos.row = 1, layout.pos.col = 1))         
print(vel, vp = viewport(layout.pos.row = 1, layout.pos.col = 2))
print(dir, vp = viewport(layout.pos.row = 2, layout.pos.col = 2))
print(hum, vp = viewport(layout.pos.row = 2, layout.pos.col = 1))
print(pre, vp = viewport(layout.pos.row = 3, layout.pos.col = 1:2))

Now I'm missing the title of the multiplot that I want to be the met. station name. I haven't found how to set main title on grid.newpage or viewport. I've read about grid.arrange but couldn't figure out how to use it in my case.

How can this be done? For sure it's gonna be an easy question for you.

You can find source data in http://ubuntuone.com/4G01ifn7cJ1jMIOKh

Thanks in advance

UPDATE: Thanks to koshke I found the solution. The working code is:

grid.newpage()
pushViewport(viewport(layout = grid.layout(4, 2, heights = unit(c(0.5, 5, 5, 5), "null"))))   
grid.text("MAIN TITLE", vp = viewport(layout.pos.row = 1, layout.pos.col = 1:2))
print(tmp, vp = viewport(layout.pos.row = 2, layout.pos.col = 1))         
print(vel, vp = viewport(layout.pos.row = 2, layout.pos.col = 2))
print(dir, vp = viewport(layout.pos.row = 3, layout.pos.col = 2))
print(hum, vp = viewport(layout.pos.row = 3, layout.pos.col = 1))
print(pre, vp = viewport(layout.pos.row = 4, layout.pos.col = 1:2))

Answer 1

library(gridExtra)

p <- ggplot()

grid.arrange(p,p,p,p,p, top = "Title",
            layout_matrix = matrix(c(1,2,3,4,5,5), ncol=2, byrow=TRUE))

Answer 2

If I understand correctly what you want to do, probably you can use +opts(title = XXX):

p1 <- ggplot(mtcars, aes(factor(cyl))) + geom_bar()
p2 <- ggplot(mtcars, aes(wt, mpg)) + geom_point()
p3 <- p2 + geom_line()

pushViewport(viewport(layout = grid.layout(2, 2)))  
print(p1 + opts(title = "bar"), 
  vp = viewport(layout.pos.row = 1, layout.pos.col = 1))     
print(p2 + opts(title = "point"), 
  vp = viewport(layout.pos.row = 1, layout.pos.col = 2))     
print(p3 + opts(title = "point and line"), 
  vp = viewport(layout.pos.row = 2, layout.pos.col = 1:2))

UPDATED

here is an example:

pushViewport(viewport(layout = grid.layout(3, 2, heights = unit(c(1, 4, 4), "null"))))
grid.text("title of this panel", vp = viewport(layout.pos.row = 1, layout.pos.col = 1:2))
print(p1, vp = viewport(layout.pos.row = 2, layout.pos.col = 1))
print(p2, vp = viewport(layout.pos.row = 2, layout.pos.col = 2))
print(p3, vp = viewport(layout.pos.row = 3, layout.pos.col = 1:2))

what you need to do is:

1. Make one extra row in grid.layout
2. Adjust width
3. Draw textGrob on the extra viewport row.

Answer 3

Nowadays you can use the really helpful package patchwork to easily combine multiple plots in one graph. To add a main title to the multiple graphs, you can use plot_annotation. Here is a reproducible example using the mtcars dataset:

library(ggplot2)
library(patchwork)
p1 <- ggplot(mtcars, aes(hp, mpg)) +           
  geom_point() +
  ggtitle("title 1")
p2 <- ggplot(mtcars, aes(qsec)) +
  geom_density() +
  ggtitle("title 2")
p3 <- ggplot(mtcars, aes(wt)) +
  geom_histogram() +
  ggtitle("title 3")
p4 <- ggplot(mtcars, aes(cyl, carb)) +
  geom_bar(stat = "identity") +
  ggtitle("title 4")

p_all <- (p1 + p2) / (p3 + p4) +    
  plot_annotation(title = "Main title of Multiplot") & 
  theme(plot.title = element_text(hjust = 0.5))

p_all 

^{Created on 2022-08-19 with reprex v2.0.2}