Chart

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"Plotting" redirects here.
An example of a pie chart, showing the composition of the 38th parliament of Canada.
A line chart showing the speed of a body versus time.

A chart or graph is a type of information graphic or graphic organizer that represents tabular numeric data and/or functions. Charts are often used to make it easier to understand large quantities of data and the relationship between different parts of the data. Charts can usually be read more quickly than the raw data that they come from. They are used in a wide variety of fields, and can be created by hand (often on graph paper) or by computer using a charting application.

Certain types of charts are more useful for presenting a given data set than others. For example, data that presents percentages in different groups (such as "satisfied, not satisfied, unsure") are often displayed in a pie chart, but some find them easier to understand when presented in a horizontal bar chart. On the other hand, data that represents numbers that change over a period of time (such as "annual revenue from 1990 to 2000") might be best shown as a line chart.

The term chart is also used when referring to a map created for navigation by air or sea. This article gives an overview of charts in the sense of graphical representations.

Comparing charts with tables

Data gathered by an observer or researcher may be presented in the form of a table or a chart (or both). Each form is useful in its own way. A table shows the precise values of data points, but from a table it is often difficult to recognize patterns or trends underlying those values. A chart, on the other hand, quickly reveals the underlying patterns. A chart is often constructed using data organized in tabular form.

Types of charts

Common charts

  • Scatter plot, scatter graph or scatter diagram: It is a type of display that uses Cartesian coordinates to show the relation between two quantitative variables. The data are displayed as a collection of points. For each point, the value of one variable determines the position on the horizontal axis, and the value of the other variable determines the position on the vertical axis.[1]
  • Line chart: A line chart is a scatter plot of ordered observations, where the observations (or points) are connected following their order. The line in a line chart depicts the best-fit trend of the scattered data.
  • Bar graph or bar chart: A bar graph uses rectangular bars to show frequencies or values for different categories. The bars can be horizontally or vertically oriented, and the lengths of the bars are proportional to the values they represent. Bar charts are used for comparing two or more values.

This bar chart shows both the results of 2004, and those of 1999:

  • Histogram: A histogram is a graphical display showing the frequencies (or proportions) of cases that fall into each of several categories. Like a bar chart, a histogram uses rectangular bars. A histogram, however, differs from a bar chart in that the area (not the height) of the bar denotes the value, a crucial distinction when the categories are not of uniform width (Lancaster, 1974). The categories are usually specified as non-overlapping intervals of some variable.
  • Pie chart or circle graph: A pie chart is a circular chart divided into sectors, illustrating relative magnitudes, frequencies, or percentages. This type of chart is named for its resemblance to a pie that has been sliced. In a pie chart, the arc length of each sector (and consequently its central angle and area) is proportional to the quantity it represents.

Less-common charts

  • A box plot (or box-and-whiskers plot) shows information about the distribution (such as minimum, maximum, mean average) along a single axis.
  • A bubble chart is a two-dimensional scatter plot in which a third variable is represented by the size of the points.
  • A doughnut chart
  • A Polar area diagram (developed by Florence Nightingale) is an enhanced form of pie chart.
  • A radar chart (or "spider chart") is a two-dimensional chart of three or more quantitative variables represented on axes starting from the same point.
  • A ternary plot is a barycentric plot on three variables which sum to a constant.
  • A waterfall chart also known as a "Walk" chart, is a special type of floating-column chart.

Field-specific charts

Some types of charts have specific uses in a certain field

  • Stock market prices are often depicted with a open-high-low-close chart with a traditional bar chart of volume at the bottom.
    • Candlestick charts are another type of bar chart used to describe price movements of an equity over time.
    • A Kagi chart is a time-independent stock tracking chart that attempts to minimise noise.
    • Alternatively, where less detail is required and chart size is paramount, a Sparkline may be used.
  • Interest rates, temperatures, etc., at the close of the period are plotted with a line chart.
  • Scatter charts plot readings of two variables simultaneously as dots between the X-axis and the Y-axis, such as for price and earnings.
  • Marketers use a lift chart to highlight performance.
  • Project planners use a Gantt chart to show the timing of tasks as they occur over time.
  • A phase diagram denotes the equilibrium conditions between thermodynamically-distinct phases.

Well-known (named) charts

Some specific charts have become well known by effectively explaining a phenomenon or idea.

  • An Allele chart is a chart originating from the study of genetics to show the interaction of two data points in a grid.
  • Bode plots are used in Control Theory.
  • The Dalitz plot is a scatterplot which represents the relative frequency of manners in which the products of certain three-body decays may move apart.
  • A Gantt chart helps in scheduling complex projects.
  • A Lineweaver-Burk plot is used to represent and determine enzyme kinetics.
  • Nichols plots are used in Control Theory.
  • The Nolan chart is a libertarian political chart.
  • Nyquist plots are used in Control Theory.
  • A PERT chart is often used in project management.
  • The Pournelle chart is a political chart to categorize state and rational ideologies.
  • The Smith chart serves in radio electronics.

See also

Notes

  1. ↑ Utts, Jessica M. 2005. Seeing Through Statistics 3rd ed. Thomson Brooks/Cole. pp 166-167. ISBN 0534394027.

References
ISBN links support NWE through referral fees

  • Bluttman, Ken. 2005. Excel Charts for Dummies. —For dummies. Hoboken, NJ: Wiley. ISBN 978-0764584732.
  • Jones, Gerald E. 2007. How to Lie with Charts. Santa Monica, CA: LaPuerta. ISBN 978-1419651434.
  • Lancaster, H.O. 1974. An Introduction to Medical Statistics. Wiley Series in Probability and Mathematical Statistics. New York: Wiley. ISBN 0471512508.
  • Zelazny, Gene. 2007. The Say It with Charts Complete Toolkit. New York: McGraw-Hill. ISBN 978-0071474702.

External links

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