Stacked bar plot Using Plotly package in R

In general, the bar plots are used to plot the categorical data. The stacked bar plot is a type of bar plot which is used to visualize the data effectively in the same bar by plotting them in a stacked manner. These are mostly used when one wants to summarize similar kinds of data by plotting a single graph. In R Programming the stacked bar plots can be plotted using the plot_ly() function of the plotly package as follows.

Syntax:

plot_ly(df,type,marker,labels,values) %>% layout() %>% add_trace()

Where,

• df: data frame
• type: used to specify the type of plot we want to visualize
• marker: used to mark the plot with different colors using color attribute
• labels: names of categorical variables in the dataset
• values: values of the columns in the dataset that we want to plot are specified here (optional)
• layout(): this function is used to change the layout as required (like assigning a title to the plot)
• add_trace(): this function is used to append similar new traces to existing dimension

Let's install and load the Plotly library with the help of the below commands

install.packages("plotly")
library(plotly)

Stack bar plot for two columns 

In this, we will be creating a data frame that contains 2 columns and then we will be using the Plotly module to plot the stacked bar plot.

data <- data.frame(
  Branches<-c('CSE','ECE','MECH','EEE','CIVIL'),
  Placements_2021 <-c(99,98,89,90,75),
  Placements_2022 <- c(95,94,93,85,77))

# Plotting the stacked bar plot using plot_ly
fig <- plotly::plot_ly(data,x = ~Branches,
                       y=~Placements_2022, type = 'bar', name = '2022') %>%
       add_trace(y=~Placements_2021,name = '2021') %>% 
       layout(yaxis = list(title = 'Placements_Count'),
              barmode = 'stack',title="Placement Statistics")
fig

Output:

Explanation:

• The plot_ly() function creates a stacked bar plot, where Branches is assigned to the x-axis and placement data to the y-axis.
• The add_trace() function is employed to add multiple layers (2021 and 2022 data).
• The layout() function customizes the appearance, such as adding a title and adjusting axis labels.

Finally, the plot is stored in the fig object, which can be shown by typing fig in the R console. 

Stack bar plot for more than two columns

We can also implement the stack bar plotting for more than 2 columns. Let's see the code for it.

# Creation of sample data frame (Student Statistics)
data <- data.frame(
  Languages<-c('Python','R','C++','Java','Ruby'),
  Batch_2020 <-c(199,398,319,910,735),
  Batch_2021 <- c(952,942,933,851,771),
  Batch_2022 <- c(1022,982,983,811,721))

# Plotting the stacked bar plot using plot_ly
fig <- plotly::plot_ly(data,x = ~Languages,y=~Batch_2020,
                       type = 'bar', name = '2020') %>%
       add_trace(y=~Batch_2021,name = '2021') %>%   
        add_trace(y=~Batch_2022,name = '2022') %>% 
       layout(yaxis = list(title = 'Students_Count'),
              barmode = 'stack',title="Student Statistics")

fig

Output:

Explanation:

• This plot illustrates student data for various programming languages across three batches (2020, 2021, and 2022).
• Multiple traces are added for different batch years, and the bars are stacked appropriately

Horizontal Stack bar plot for more than two columns

Now we can try to plot a stack bar plot in the horizontal direction.

data <- data.frame(
  Languages = c('Python', 'R', 'C++', 'Java', 'Ruby'),
  Batch_2020 = c(199, 398, 319, 910, 735),
  Batch_2021 = c(952, 942, 933, 851, 771),
  Batch_2022 = c(1022, 982, 983, 811, 721)
)

# Plotting the horizontal stacked bar plot using plot_ly
fig <- plotly::plot_ly(data, y = ~Languages, x = ~Batch_2020,
                       type = 'bar', name = '2020', orientation = 'h') %>%
  add_trace(y = ~Languages, x = ~Batch_2021, name = '2021', orientation = 'h') %>%
  add_trace(y = ~Languages, x = ~Batch_2022, name = '2022', orientation = 'h') %>%
  layout(
    xaxis = list(title = 'Students Count'),
    barmode = 'stack',
    title = "Student Statistics",
    yaxis = list(title = 'Languages'),
    legend = list(title = 'Batches', orientation = 'v', 
                  xanchor = 'center', x = 0.5, y = -0.2)
  )
fig

Output:

Explanation:

• By making the orientation parameter equal to 'h', the bars are shown horizontally.
• The legend and axes are reoriented to accommodate the new orientation, and a good visualization of the data is provided.