IGCSE ICT 0417 - Graphs and Charts

16. Adding a Second Data Series

This section explains how to add a second data series to a graph or chart. This is useful for comparing two different sets of data on the same visual representation. We will cover the steps involved and consider different types of charts where this is applicable.

When to Add a Second Data Series

Adding a second data series is beneficial when:

• You want to compare two different sets of data on the same scale.
• You need to show the relationship between two different variables.
• You want to highlight trends in two related datasets.

Chart Types Suitable for Multiple Data Series

The following chart types are commonly used to display multiple data series:

• Line Graphs: Excellent for comparing trends over time.
• Bar Charts: Useful for comparing categorical data across multiple categories.
• Line and Bar Charts: Can combine the strengths of both chart types.
• Scatter Plots: Can be used to plot two different datasets against the same variable.

Steps to Add a Second Data Series (General Guide - using spreadsheet software like Excel or Google Sheets)

1. Prepare Your Data: Ensure your data is organized in columns. One column for each data series and rows for each point.
2. Select Your Chart: Create the initial chart with your first data series.
3. Select the Second Data Series: Select the column containing the data for your second series.
4. Add the Data Series: This is usually done by right-clicking on the chart and selecting "Select Data" or a similar option. In the 'Select Data Source' dialog, you'll find an option to add a new series.
5. Specify the Series Name: Give the second data series a descriptive name. This will appear in the legend.
6. Customize the Chart: Adjust the chart title, axis labels, legend, and colors to make it clear and easy to understand.

Example: Line Graph with Two Data Series

Let's consider an example of a line graph showing the sales of two different products over a period of months.

Month	Product A Sales	Product B Sales
January	100	150
February	120	130
March	110	160
April	130	140
May	140	170

Figure: Suggested diagram: A line graph with 'Month' on the X-axis and 'Sales' on the Y-axis. Two lines are plotted: one for 'Product A Sales' and one for 'Product B Sales'. A legend clearly identifies each line.

Steps to create this graph in a spreadsheet program:

1. Enter the data above into a spreadsheet.
2. Select the data (including headers).
3. Insert a line chart.
4. Right-click on the chart and select "Select Data".
5. Add "Product B Sales" as a second series, naming it "Product B".
6. Customize the chart with appropriate titles and labels.

Important Considerations

When adding a second data series:

• Use different colors or line styles: This helps distinguish between the two series.
• Ensure clear labels: The legend should clearly identify each series.
• Choose appropriate scales: The Y-axis scale should accommodate both data series without one being compressed or excessively large.
• Avoid clutter: Too many data series can make a chart difficult to read. Consider whether all series are necessary.