I am trying to display some information about the data below the plot created in ggplot2. I would like to plot the N variable using the X axis coordinate of the plot but the Y coordinate needs to be 10% from the bottom of the screen . In fact, the desired Y coordinates are already in the data frame as y_pos variable.
I can think of 3 approaches using ggplot2:
1) Create an empty plot below the actual plot, use the same scale and then use geom_text to plot the data over the blank plot. This approach sort of works but is extremely complicated.
2) Use geom_text to plot the data but somehow use y coordinate as percent of the screen (10%). This would force the numbers to be displayed below the plot. I can't figure out the proper syntax.
3) Use grid.text to display the text. I can easily set it at the 10% from the bottom of the screen but I can't figure how set the X coordindate to match the plot. I tried to use grconvert to capture the initial X position but could not get that to work as well.
Below is the basic plot with the dummy data:
graphics.off() # close graphics windows
library(car)
library(ggplot2) #load ggplot
library(gridExtra) #load Grid
library(RGraphics) # support of the "R graphics" book, on CRAN
#create dummy data
test= data.frame(
Group = c("A", "B", "A","B", "A", "B"),
x = c(1 ,1,2,2,3,3 ),
y = c(33,25,27,36,43,25),
n=c(71,55,65,58,65,58),
y_pos=c(9,6,9,6,9,6)
)
#create ggplot
p1 <- qplot(x, y, data=test, colour=Group) +
ylab("Mean change from baseline") +
geom_line()+
scale_x_continuous("Weeks", breaks=seq(-1,3, by = 1) ) +
opts(
legend.position=c(.1,0.9))
#display plot
p1
The modified gplot below displays numbers of subjects, however they are displayed WITHIN the plot. They force the Y scale to be extended. I would like to display these numbers BELOW the plot.
p1 <- qplot(x, y, data=test, colour=Group) +
ylab("Mean change from baseline") +
geom_line()+
scale_x_continuous("Weeks", breaks=seq(-1,3, by = 1) ) +
opts( plot.margin = unit(c(0,2,2,1), "lines"),
legend.position=c(.1,0.9))+
geom_text(data = test,aes(x=x,y=y_pos,label=n))
p1
A different approach of displaying the numbers involves creating a dummy plot below the actual plot. Here is the code:
graphics.off() # close graphics windows
library(car)
library(ggplot2) #load ggplot
library(gridExtra) #load Grid
library(RGraphics) # support of the "R graphics" book, on CRAN
#create dummy data
test= data.frame(
group = c("A", "B", "A","B", "A", "B"),
x = c(1 ,1,2,2,3,3 ),
y = c(33,25,27,36,43,25),
n=c(71,55,65,58,65,58),
y_pos=c(15,6,15,6,15,6)
)
p1 <- qplot(x, y, data=test, colour=group) +
ylab("Mean change from baseline") +
opts(plot.margin = unit(c(1,2,-1,1), "lines")) +
geom_line()+
scale_x_continuous("Weeks", breaks=seq(-1,3, by = 1) ) +
opts(legend.position="bottom",
legend.title=theme_blank(),
title.text="Line plot using GGPLOT")
p1
p2 <- qplot(x, y, data=test, geom="blank")+
ylab(" ")+
opts( plot.margin = unit(c(0,2,-2,1), "lines"),
axis.line = theme_blank(),
axis.ticks = theme_segment(colour = "white"),
axis.text.x=theme_text(angle=-90,colour="white"),
axis.text.y=theme_text(angle=-90,colour="white"),
panel.background = theme_rect(fill = "transparent",colour = NA),
panel.grid.minor = theme_blank(),
panel.grid.major = theme_blank()
)+
geom_text(data = test,aes(x=x,y=y_pos,label=n))
p2
grid.arrange(p1, p2, heights = c(8.5, 1.5), nrow=2 )
However, that is very complicated and would be hard to modify for different data. Ideally, I'd like to be able to pass Y coordinates as percent of the screen.
