ggplot side by side geom_bar()

Question

I want to create a side by side barplot using geom_bar() of this data frame,

> dfp1
   value   percent1   percent
1 (18,29] 0.20909091 0.4545455
2 (29,40] 0.23478261 0.5431034
3 (40,51] 0.15492958 0.3661972
4 (51,62] 0.10119048 0.1726190
5 (62,95] 0.05660377 0.1194969

With values on the x-axis and the percents as the side by side barplots. I have tried using this code,

p = ggplot(dfp1, aes(x = value, y= c(percent, percent1)), xlab="Age Group")
p = p + geom_bar(stat="identity", width=.5)  

However, I get this error: Error: Aesthetics must either be length one, or the same length as the dataProblems:value. My percent and percent1 are the same length as value, so I am confused. Thanks for the help.

Answer 1

You will need to melt your data first over value. It will create another variable called value by default, so you will need to renames it (I called it percent). Then, plot the new data set using fill in order to separate the data into groups, and position = "dodge" in order put the bars side by side (instead of on top of each other)

library(reshape2)
library(ggplot2)
dfp1 <- melt(dfp1)
names(dfp1)[3] <- "percent"
ggplot(dfp1, aes(x = value, y= percent, fill = variable), xlab="Age Group") +
   geom_bar(stat="identity", width=.5, position = "dodge")