How To Make A Segmented Bar Graph

Segmented bar graphs, also known as stacked bar charts, are powerful visualization tools that allow you to compare the composition of different categories. They display data as horizontal or vertical bars, with each bar representing a total and divided into segments showing the proportion of different sub-categories within that total. This type of chart is particularly useful when you want to understand both the overall values of different categories and the relative contribution of their components.

Why Use a Segmented Bar Graph?

Segmented bar graphs offer several advantages for data visualization:

• Comparative Analysis: They allow for a direct comparison of the total values across different categories.
• Composition Breakdown: They clearly display the proportion of each sub-category within each category, providing insights into the composition of each total.
• Trend Identification: They can be used to identify trends and patterns in the data, particularly when the data is displayed over time.
• Visual Impact: They are visually appealing and easy to understand, making them effective for communicating complex data to a wide audience.

When to Avoid Segmented Bar Graphs

While useful, segmented bar graphs aren't always the best choice:

• Too Many Segments: If a bar has too many segments, it can become difficult to read and interpret. Consider using a different chart type, such as a grouped bar chart or a pie chart, if you have more than 5-7 segments per bar.
• Focus on Exact Values: Segmented bar graphs are better for showing proportions rather than exact values. If the exact values are critical, a table or a different chart type might be more appropriate.
• Negative Values: Segmented bar graphs are not suitable for displaying negative values.

Tools for Creating Segmented Bar Graphs

Several tools are available for creating segmented bar graphs, ranging from spreadsheet software to specialized data visualization platforms:

• Microsoft Excel: Excel offers basic charting capabilities, including the ability to create segmented bar graphs. It's a readily available option for many users.
• Google Sheets: Similar to Excel, Google Sheets provides a free and accessible platform for creating charts, including segmented bar graphs.
• Tableau: Tableau is a powerful data visualization tool that offers a wide range of charting options, including advanced customization features for segmented bar graphs.
• Power BI: Microsoft's Power BI is another popular data visualization platform that excels at creating interactive and insightful charts, including segmented bar graphs.
• Python (with libraries like Matplotlib and Seaborn): For more advanced users, Python libraries like Matplotlib and Seaborn provide a highly flexible and customizable environment for creating segmented bar graphs.
• R (with libraries like ggplot2): R is another powerful statistical programming language with excellent data visualization capabilities through libraries like ggplot2.
• Online Chart Makers: Numerous online tools like Chart Maker, Canva, and others offer user-friendly interfaces for creating various chart types, including segmented bar graphs.

Step-by-Step Guide to Creating a Segmented Bar Graph in Excel

This guide will walk you through the process of creating a segmented bar graph in Microsoft Excel.

1. Prepare Your Data:

The first step is to organize your data in a way that Excel can understand. Your data should consist of:

• Categories: These are the main groups you want to compare (e.g., different years, product lines, regions).
• Sub-Categories: These are the components that make up each category (e.g., different product types, departments, age groups).
• Values: These are the numerical values associated with each sub-category within each category.

Here's an example of how your data might look in Excel:

2. Select Your Data:

Select the entire data range, including the headers (Category, Sub-Category, Value).

3. Insert a Stacked Bar Chart:

• Go to the "Insert" tab on the Excel ribbon.
• In the "Charts" group, click on the "Insert Bar Chart" dropdown.
• Choose either "Stacked Bar" (for horizontal bars) or "Stacked Column" (for vertical bars). Select the one that best suits your data and desired presentation.

4. Customize Your Chart:

Excel will automatically create a basic segmented bar graph. Now, you can customize it to make it more visually appealing and informative. Here are some common customizations:

• Chart Title: Double-click on the chart title to edit it. Give your chart a clear and descriptive title that explains what the chart is showing.
• Axis Titles: Add axis titles to the horizontal and vertical axes to indicate what they represent (e.g., "Year" for the category axis and "Sales (USD)" for the value axis). To add axis titles:
  • Click on the chart.
  • Click the "+" icon that appears to the top right of the chart.
  • Check the "Axis Titles" box.
  • Double-click on each axis title to edit it.
• Legend: The legend identifies the different sub-categories. You can change its position, appearance, and labels. To format the legend:
  • Click on the legend.
  • Right-click and choose "Format Legend."
  • In the "Format Legend" pane, you can adjust the position, fill, border, and other properties.
• Data Labels: Add data labels to the segments to show the exact values or percentages. To add data labels:
  • Click on the chart.
  • Click the "+" icon that appears to the top right of the chart.
  • Check the "Data Labels" box.
  • To format the data labels (e.g., change the number format, position, or font), click on the data labels, right-click, and choose "Format Data Labels."
• Colors: Change the colors of the segments to make the chart more visually appealing and easier to understand. To change the color of a segment:
  • Click on the segment you want to change.
  • Right-click and choose "Format Data Point."
  • In the "Format Data Point" pane, go to the "Fill & Line" section and choose a new color.
• Gap Width: Adjust the gap width between the bars to control the spacing. To adjust the gap width:
  • Click on any of the bars.
  • Right-click and choose "Format Data Series."
  • In the "Format Data Series" pane, adjust the "Gap Width" setting. A smaller gap width will make the bars wider, while a larger gap width will make them narrower.
• Switch Row/Column: If your data is organized with categories in rows and sub-categories in columns, you might need to switch the row/column orientation of the chart. To do this:
  • Click on the chart.
  • Go to the "Chart Design" tab on the Excel ribbon.
  • Click on the "Switch Row/Column" button.
• Chart Styles: Excel provides pre-designed chart styles that can quickly change the overall look and feel of your chart. To apply a chart style:
  • Click on the chart.
  • Go to the "Chart Design" tab on the Excel ribbon.
  • Browse through the chart styles in the "Chart Styles" gallery and choose one that you like.

5. Consider a 100% Stacked Bar Chart:

If your primary goal is to compare the proportions of sub-categories within each category, rather than the absolute values, a 100% stacked bar chart might be more appropriate. This type of chart displays each bar as 100%, with the segments representing the percentage contribution of each sub-category. To create a 100% stacked bar chart:

• Follow the same steps as above, but instead of choosing "Stacked Bar" or "Stacked Column," choose "100% Stacked Bar" or "100% Stacked Column."

Example Customization Steps:

Let's say you want to:

• Change the chart title to "Sales by Product Type (2021-2023)"
• Add axis titles "Year" (horizontal) and "Sales (USD)" (vertical)
• Add data labels showing the sales value for each segment
• Change the color of the "Electronics" segments to blue
• Reduce the gap width between the bars

Here's how you would do it:

1. Chart Title: Double-click on the chart title and type "Sales by Product Type (2021-2023)".
2. Axis Titles: Click the "+" icon, check "Axis Titles", then edit the titles to "Year" and "Sales (USD)".
3. Data Labels: Click the "+" icon and check "Data Labels". Right-click on the data labels and choose "Format Data Labels" to customize the number format if needed.
4. Color Change: Click on one of the "Electronics" segments. All "Electronics" segments should be selected. Right-click and choose "Format Data Point." In the "Fill & Line" pane, choose a blue color.
5. Gap Width: Click on any of the bars. Right-click and choose "Format Data Series." In the "Format Data Series" pane, decrease the "Gap Width" value.

6. Save Your Chart:

Once you're satisfied with your chart, you can save it as part of your Excel workbook. You can also copy and paste the chart into other applications, such as Word documents or PowerPoint presentations.

Example using Python with Matplotlib

Here's an example of creating a segmented bar graph using Python with the Matplotlib library:

import matplotlib.pyplot as plt
import numpy as np

# Sample data
categories = ['Category A', 'Category B', 'Category C']
sub_categories = ['Sub-Category 1', 'Sub-Category 2', 'Sub-Category 3']
data = np.array([[10, 20, 30],
                 [15, 25, 35],
                 [20, 30, 40]])

# Create the segmented bar graph
fig, ax = plt.subplots()

# Calculate cumulative sums for the bottom of each segment
cumulative_sum = np.zeros(len(categories))

# Iterate through each sub-category
for i, sub_category in enumerate(sub_categories):
    # Plot the bars for the current sub-category
    ax.bar(categories, data[i], bottom=cumulative_sum, label=sub_category)
    # Update the cumulative sum for the next sub-category
    cumulative_sum += data[i]

# Add labels and title
ax.set_xlabel('Categories')
ax.set_ylabel('Values')
ax.set_title('Segmented Bar Graph Example')
ax.legend()

# Show the plot
plt.show()

This code will generate a segmented bar graph with three categories (Category A, Category B, and Category C) and three sub-categories (Sub-Category 1, Sub-Category 2, and Sub-Category 3). The data array defines the values for each sub-category within each category. The code iterates through each sub-category and plots a bar for each category, using the bottom parameter to stack the bars on top of each other.

Best Practices for Segmented Bar Graphs

To create effective segmented bar graphs, keep these best practices in mind:

• Keep it Simple: Avoid using too many sub-categories, as this can make the chart difficult to read. Aim for a maximum of 5-7 segments per bar.
• Use Clear Labels: Make sure your chart title, axis titles, and legend labels are clear and descriptive.
• Choose Appropriate Colors: Select colors that are visually distinct and easy on the eyes. Consider using a color palette that is accessible to people with color blindness.
• Order Sub-Categories Logically: Order the sub-categories in a way that makes sense for your data. For example, you might order them by size, alphabetically, or by a specific category.
• Consider a 100% Stacked Bar Chart: If your focus is on comparing proportions, a 100% stacked bar chart can be more effective than a standard segmented bar graph.
• Provide Context: In addition to the chart itself, provide context and analysis to help your audience understand the data. Explain the key trends and patterns that you observe in the chart.
• Avoid 3D Effects: 3D effects can distort the perception of the data and make the chart more difficult to read. Stick to 2D charts for clarity.
• Check for Accuracy: Double-check your data and chart to ensure that they are accurate and free of errors.

Common Mistakes to Avoid

• Using Too Many Categories or Sub-Categories: Overcrowding the chart makes it difficult to interpret.
• Misleading Scales: Ensure the axes are scaled appropriately to accurately represent the data. Avoid truncated axes that can exaggerate differences.
• Inconsistent Color Schemes: Use a consistent color scheme throughout the chart and avoid using colors that are too similar or clash with each other.
• Ignoring the Target Audience: Tailor the chart's design and complexity to the knowledge level of your audience.
• Forgetting to Label Units: Always include units (e.g., USD, %, kg) on the axes and data labels for clarity.
• Not Providing a Clear Narrative: A segmented bar graph should tell a story. Make sure the title, labels, and accompanying text clearly communicate the key insights.

Alternative Chart Types

If a segmented bar graph isn't the best choice for your data, consider these alternative chart types:

• Grouped Bar Chart: This chart displays bars for each sub-category side-by-side, allowing for easy comparison of individual values.
• Pie Chart: Pie charts are useful for showing the proportion of different parts of a whole, but they can be difficult to read if there are too many slices.
• Line Chart: Line charts are ideal for showing trends over time.
• Area Chart: Area charts are similar to line charts, but they fill the area under the line, which can be useful for emphasizing the magnitude of the values.
• Table: Sometimes, a simple table is the most effective way to present data, especially if the exact values are important.

Conclusion

Segmented bar graphs are a valuable tool for visualizing data and comparing the composition of different categories. By following the steps and best practices outlined in this guide, you can create effective and informative segmented bar graphs that communicate your data clearly and persuasively. Remember to choose the right tool for the job, prepare your data carefully, customize your chart to make it visually appealing, and provide context to help your audience understand the data. Consider the alternatives if a segmented bar chart isn't the most suitable option. By avoiding common mistakes and focusing on clarity and accuracy, you can create segmented bar graphs that provide valuable insights and support informed decision-making.