Dynamic data labels in geom_bar

Question

I am using ggplot2 geom_bar to make a series of bar charts. Each city has three data points, and I am making a graph for each city. I want to label the second and third bar in each chart as a percent of the previous bar (e.g. data that looks like 5, 4, 3 would read 5, 80%, 75%).

In this data, I am value should be the label for bar 1 in all graphs. dum2/dum1*100 should be the label for the bar with the value of dum2. dum3/dum2*100 should be the label for the bar with value dum3.

Example

State <- c("AA","AB","AC","AD","AE")
dum1 <- c(34, 30, 8, 22, 5)
dum2 <- c(22.5, 28.1, 3, 12, 1)
dum3 <- c(12.8, 23, 2.8, 11.9, 0.3)
df <- data.frame(State, dum1, dum2, dum3)
m1 <-melt(df)

for(i in levels(m1$State)) 
p <- ggplot(subset(m1, State==i), aes(variable, value,  fill = variable)) +
facet_wrap(~ State) + 
geom_bar(stat="identity", show_guide=FALSE) + 
geom_text(aes(x=variable, y=value + 2, label=round(value,digits=0)), vjust=0,
        size=30) +
theme(axis.title.x = element_blank(),
    plot.background = element_rect(fill = "transparent", color=NA),
    panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
    panel.border = element_blank(), panel.background = element_blank(),
    axis.line = element_blank(), axis.title.y=element_blank(),
    axis.line = element_blank(), 
    axis.text.x = element_blank(), 
    axis.text.y = element_blank(),
    axis.ticks = element_blank(), 
    axis.title.y = element_blank(),
    strip.text.x = element_blank(),
    strip.background = element_rect(fill="transparent")
     ) +
     scale_y_continuous(limits=c(0,40)) +
    scale_fill_manual(values=c("navy", "coral", "gold")) +
  ggsave(sprintf("plot %s.jpg", i))

I have tried adding in a column with the calculated percent for the relevant rows, but don't know how to call a column for only selected data points on the graph. I used something like

lab<-c(0,0,0,0,0,66.2,93.7,37.5,54.5,20.0,56.9,81.9,93.3,99.2,30.0)

but cannot figure out how to call it appropriately for the correct bars.

why not just replace the 0s with the numbers that the first bars should be labeled with? eg lab <- round ( c (dum1, dum2/dum1*100, dum3/dum2*100), 1) — janattack

jlhoward jlhoward · Accepted Answer · 2015-10-28T05:13:12

Without all the extraneous formatting, this seems to do what you are asking:

ggplot(subset(m1, State=="AA"), aes(variable, value,  fill = variable)) +
  facet_wrap(~ State) + 
  geom_bar(stat="identity", show_guide=FALSE) + 
  geom_text(aes(x=variable, y=value + 2, 
                label=paste0(round(value/c(1,0.01*head(value,-1))),c("","%","%"))))

Dynamic data labels in geom_bar

1 Answers