ggplot: conflict between geom_text and ggplot(fill)

Question

When I use geom_text on a ggplot, there is a conflict with the ggplot "fill" option.

Here is a clear example of the problem:

library(ggplot2)
a=ChickWeight
str(a)
xx=data.frame(level=levels(a$Chick),letter=1:50)

# a graph with the fill option alone
x11();ggplot(a, aes(x=Chick, y=weight,fill=Diet))  + geom_boxplot(notch=F) +
stat_summary(fun.y="mean", geom="point", shape=23, size=3, fill="white") +
xlab("Chick") +
ylab("Weight")

# a graph with the geom_text option alone
x11();ggplot(a, aes(x=Chick, y=weight))  + geom_boxplot(notch=F) +
stat_summary(fun.y="mean", geom="point", shape=23, size=3, fill="white") +
geom_text(data=xx, aes(x=level,y=450,label = letter)) +
xlab("Chick") +
ylab("Weight")

# a graph with the two option
x11();ggplot(a, aes(x=Chick, y=weight,fill=Diet))  + geom_boxplot(notch=F) +
stat_summary(fun.y="mean", geom="point", shape=23, size=3, fill="white") +
geom_text(data=xx, aes(x=level,y=1750,label = letter)) +
xlab("Chick") +
ylab("Weight")

Answer 1

If you only want the fill to affect the boxplot, move the aes() into the boxplot. Any aes() aesthetics in the ggplot() call itself will be propagated to all layers

ggplot(a, aes(x=Chick, y=weight))  + geom_boxplot(aes(fill=Diet), notch=F) +
stat_summary(fun.y="mean", geom="point", shape=23, size=3, fill="white") +
geom_text(data=xx, aes(x=level,y=1750,label = letter)) +
xlab("Chick") +
ylab("Weight")

you can also disable the fill= aesthetic in the text layer with fill=NULL

ggplot(a, aes(x=Chick, y=weight, fill=Diet))  + geom_boxplot(notch=F) +
stat_summary(fun.y="mean", geom="point", shape=23, size=3, fill="white") +
geom_text(data=xx, aes(x=level,y=1750,label = letter, fill=NULL)) +
xlab("Chick") +
ylab("Weight")