Grouped bar chart on R using ggplot2

Question

How do I create a grouped bar chart on R using ggplot2 using this data?

Person Cats Dogs

Mr. A   3   1

Mr. B   4   2

So that it shows that shows number of pets owned per person, with this layout Bar chart of pets

I have a text file with this data and have used read.delim to read the file on R.

I have used this code but it does not produce the bar plot I am looking for.

ggplot(data=pets, aes(x=Person, y=Cats, fill=Dogs)) + geom_bar(stat="identity", position=position_dodge())

I am new to R, any help would be appreciated.

Thanks in advance.

Solution

To prepare data for grouped bar plot, use melt() function of reshape2 package

I. Loading required packages

    library(reshape2)
    library(ggplot2)

II. Creating data frame df

    df <- data.frame(Person = c("Mr.A","Mr.B"), Cats = c(3,4), Dogs = c(1,2))
    df
    #   Person Cats Dogs
    # 1   Mr.A    3    1
    # 2   Mr.B    4    2

III. Melting data using melt function

    data.m <- melt(df, id.vars='Person')
    data.m
    #   Person variable value
    # 1   Mr.A     Cats     3
    # 2   Mr.B     Cats     4
    # 3   Mr.A     Dogs     1
    # 4   Mr.B     Dogs     2

IV. Grouped Bar plot by Person

   ggplot(data.m, aes(Person, value)) + geom_bar(aes(fill = variable), 
   width = 0.4, position = position_dodge(width=0.5), stat="identity") +  
   theme(legend.position="top", legend.title = 
   element_blank(),axis.title.x=element_blank(), 
   axis.title.y=element_blank())

Legend on top, legend title removed, axis titles removed, adjusted bar widths and space between bars.

Comments

[CroatiaHR]

by far the best explanation that I have found by now online