How to prevent two labels to overlap in a barchart?

Question

The image below shows a chart that I created with the code below. I highlighted the missing or overlapping labels. Is there a way to tell ggplot2 to not overlap labels?

week = c(0, 1, 1, 1, 1, 2, 2, 3, 4, 5)
statuses = c('Shipped', 'Shipped', 'Shipped', 'Shipped', 'Not-Shipped', 'Shipped', 'Shipped', 'Shipped', 'Not-Shipped', 'Shipped')

dat <- data.frame(Week = week, Status = statuses)

p <- qplot(factor(Week), data = dat, geom = "bar", fill = factor(Status))
p <- p + geom_bar()
# Below is the most important line, that's the one which displays the value
p <- p + stat_bin(aes(label = ..count..), geom = "text", vjust = -1, size = 3)
p

Answer 1

You can use a variant of the well-known population pyramid.

Some sample data (code inspired by Didzis Elferts' answer):

set.seed(654)
week <- sample(0:9, 3000, rep=TRUE, prob = rchisq(10, df = 3))
status <- factor(rbinom(3000, 1, 0.15), labels = c("Shipped", "Not-Shipped"))
data.df <- data.frame(Week = week, Status = status)

Compute count scores for each week, then convert one category to negative values:

library("plyr")
plot.df <- ddply(data.df, .(Week, Status), nrow)
plot.df$V1 <- ifelse(plot.df$Status == "Shipped",
                     plot.df$V1, -plot.df$V1)

Draw the plot. Note that the y-axis labels are adapted to show positive values on either side of the baseline.

library("ggplot2")
ggplot(plot.df) + 
  aes(x = as.factor(Week), y = V1, fill = Status) +
  geom_bar(stat = "identity", position = "identity") +
  scale_y_continuous(breaks = 100 *     -1:5, 
                     labels = 100 * c(1, 0:5)) +
  geom_text(aes(y = sign(V1) * max(V1) / 30, label = abs(V1)))

The plot:

For production purposes you'd need to determine the appropriate y-axis tick labels dynamically.

Answer 2

Made new sample data (inspired by code of @agstudy).

week <- sample(0:5,1000,rep=TRUE,prob=c(0.2,0.05,0.15,0.5,0.03,0.1))
statuses <- gl(2,1000,labels=c('Not-Shipped', 'Shipped'))
dat <- data.frame(Week = week, Status = statuses)

Using function ddply() from library plyr made new data frame text.df for labels. Column count contains number of observations in each combination of Week and Status. Then added column ypos that contains cumulative sum of count for each Week plus 15. This will be used for y position. For Not-Shipped ypos replaced with -10.

library(plyr)
text.df<-ddply(dat,.(Week,Status),function(x) data.frame(count=nrow(x)))
text.df<-ddply(text.df,.(Week),transform,ypos=cumsum(count)+15)
text.df$ypos[text.df$Status=="Not-Shipped"]<- -10

Now labels are plotted with geom_text() using new data frame.

ggplot(dat,aes(as.factor(Week),fill=Status))+geom_bar()+
  geom_text(data=text.df,aes(x=as.factor(Week),y=ypos,label=count))

Answer 3

One solution to avoid overlaps is to use to dodge position of bars and texts. To avoid missing values you can set ylim. Here an example.

##  I create some more realistic data similar to your picture
week <- sample(0:5,1000,rep=TRUE)
statuses <- gl(2,1000,labels=c('Not-Shipped', 'Shipped'))
dat <- data.frame(Week = week, Status = statuses)

## for dodging
dodgewidth <- position_dodge(width=0.9)
## get max y to set ylim
ymax <- max(table(dat$Week,dat$Status))+20
ggplot(dat,aes(x = factor(Week),fill = factor(Status))) + 
  geom_bar( position = dodgewidth ) +
  stat_bin(geom="text", position= dodgewidth, aes( label=..count..),
           vjust=-1,size=5)+
  ylim(0,ymax)