How to get a barplot with several variables side by side grouped by a factor

Question

I have a dataset which looks like this one below. I am trying to make a barplot with the grouping variable gender, with all the variables side by side on the x axis (grouped by gender as filler with different colors), and mean values of variables on the y axis (which basically represents percentages)

tea                coke            beer             water           gender 14.55              26.50793651     22.53968254      40              1 24.92997199        24.50980392     26.05042017      24.50980393     2 23.03732304        30.63063063     25.41827542      20.91377091     1    225.51781276       24.6064623      24.85501243      50.80645161     1 24.53662842        26.03706973     25.24271845      24.18358341     2    

In the end I want to get a barplot like this

any suggestions how to do that? I made some searches but I only find examples for factors on the x axis, not variables grouped by a factor. any help will be appreciated!

Answer 1

You can use aggregate to calculate the means:

means<-aggregate(df,by=list(df$gender),mean) Group.1      tea     coke     beer    water gender 1       1 87.70171 27.24834 24.27099 37.24007      1 2       2 24.73330 25.27344 25.64657 24.34669      2 

Get rid of the Group.1 column

means<-means[,2:length(means)] 

Then you have reformat the data to be in long format:

library(reshape2) means.long<-melt(means,id.vars="gender")   gender variable    value 1      1      tea 87.70171 2      2      tea 24.73330 3      1     coke 27.24834 4      2     coke 25.27344 5      1     beer 24.27099 6      2     beer 25.64657 7      1    water 37.24007 8      2    water 24.34669 

Finally, you can use ggplot2 to create your plot:

library(ggplot2) ggplot(means.long,aes(x=variable,y=value,fill=factor(gender)))+   geom_bar(stat="identity",position="dodge")+   scale_fill_discrete(name="Gender",                       breaks=c(1, 2),                       labels=c("Male", "Female"))+   xlab("Beverage")+ylab("Mean Percentage")