A Picture Is Worth a Thousand Words - Understanding Basic Types of Charts and Graphs
by LogiXML BIz Comm Editorial Staff
November 1, 2006
No reporting and analysis solution is complete without providing ways to visualize information. Charts and graphs help users to better understand their data and provide a fast, more meaningful view in context, especially when comparing data. There are a myriad of different charts and graphs. So, which is better for which purpose?
This article explores some of the more commonly used chart and graph types and describes the types of data presentations and analysis they are most useful for.
Pie Charts
Pie Charts are helpful for viewing proportions or percentages. They visually represent the contribution of each value to a total sum of data, or the component parts of the whole.
Pie charts can be used for any report that can use percentages to compare information. Just a few examples include:
- Product sales distribution
- Budget allocations
- Revenue distribution
Line Charts
Line charts can display large amounts of data that varies along some accepted sequence such as time, temperature, price, etc. Line charts are useful for determining trends. Line charts with multiple lines can be used to compare more than one dependent variable on a single scale.
Line charts are very popular because they clearly reveal data trends and are easy to create.
A Spline Chart is similar to a Line Chart; the only difference being the way in which the points of a series are connected. It plots one or several series of data and joins each series by smooth spline curves instead of straight lines.
Line and spline charts are especially useful in the fields of statistics and science, and can be used for the following scenarios among many others:
- Determining trends or cyclical variations
- Money distribution over time
- Production over time
- Price variation over time
- Environmental changes over time
- Clinical responses by concentration
Area Charts
Area charts emphasize magnitude of change over time and can be used to draw attention to the total value across a trend. For example, data that represents profit over time can be plotted in an area chart to emphasize the total profit.
By displaying the sum of the plotted values, an area chart also shows the relationship of parts to a whole.
Area charts are used to display data sets on an X-Y axis with the area under the line filled. The values for each area reflect the cumulative value of the data element rather than the individual value for each data element.
A few examples of how area charts can be used include:
- Display changes in cumulative values or percentages over time
- Compare groups on outcome measurements
- Display group trends
Vertical and Horizontal Bar Charts
Vertical and horizontal bar charts, like pie charts, are useful for comparing data. But they are also used to compare values across categories or to compare the contribution of each value to a total across categories (e.g., stacked bars).
Bar charts can have a single category of data, or they can be broken down further into multiple categories for greater depth of analysis.
Vertical bar charts are useful for showing time series data. The space for labels on the x-axis is small, but ideal for years, minutes, hours or months. At a glance you can see from the graph that the scales for both the x- and y-axis increase as they get farther away from the origin. The horizontal bar graph uses the y-axis (vertical line) for labeling, and there
is more room to fit text labels for variables on the y-axis.
 
Scatter Charts
Scatter charts visually display relationships between two or three sets of values with the third value displayed as a relative size of the scatter mark.
The pattern of the data points on the scatter plot reveals the relationship between the variables. Scatterplots can illustrate various patterns and relationships, such as:
- data correlation
- positive or direct relationships between variables
- negative or inverse relationships between variables
- scattered data points
- non-linear patterns
- outliers
Further Reading
For more information about using the right chart to convey your information, there are many detailed reference books to help, including the following:
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