How to make the best use of graphics: Line graphs

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First Published: 
Jan 2007
Updated: 

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Key Learnings contained in this article:

Line graphs are an extremely useful way of showing changes and trends, especially over time. The following pointers are helpful when considering the use of line graphs:

  • Use when graphing a continuous variable by a continuous variable. A common example is a time series. In a graph of a time series, time should run horizontally.
  • Display a maximum of three dependent variables (as lines) on any one graph. Otherwise the graph can become crowded and difficult to read.
  • Use a different line style for each variable, even if the lines are also distinguished by colour. This facilitates black-and-white printing and photocopying.
  • Where multiple lines overlap such that they are difficult to distinguish, consider using more than one graph to display the data, or perhaps a grouped bar graph.
  • Consider using a vertical bar graph for time series where the series is short and the message relates to comparison of individual quantities (e.g. yearly results) rather than to changes.
  • Where there is a visible seasonal component in a time series then at least two years’ data should be graphed, or the seasonal component of the variation may be mistaken for a trend.
  • Equal intervals (of time, for example) should be equally spaced.
  • Where there is a discontinuity in the data do not join the points across the discontinuity, and explain this in the caption.

Line graphs are an extremely useful way of showing changes and trends, especially over time. The following pointers are helpful when considering the use of line graphs:

  • Use when graphing a continuous variable by a continuous variable. A common example is a time series. In a graph of a time series, time should run horizontally.
  • Display a maximum of three dependent variables (as lines) on any one graph. Otherwise the graph can become crowded and difficult to read.
  • Use a different line style for each variable, even if the lines are also distinguished by colour. This facilitates black-and-white printing and photocopying.
  • Where multiple lines overlap such that they are difficult to distinguish, consider using more than one graph to display the data, or perhaps a grouped bar graph.
  • Consider using a vertical bar graph for time series where the series is short and the message relates to comparison of individual quantities (e.g. yearly results) rather than to changes.
  • Where there is a visible seasonal component in a time series then at least two years’ data should be graphed, or the seasonal component of the variation may be mistaken for a trend.
  • Equal intervals (of time, for example) should be equally spaced.
  • Where there is a discontinuity in the data do not join the points across the discontinuity, and explain this in the caption.

Things you should know about Journals...

To support you in this, we've prepared a number of articles to assist you in making the right journal selection for your publication. If you would like a broad overview, start with our comprehensive article 'Navigating the Journal Selection & Submission Process', or jump in to one of these other related topics and get the information you need to be successful!
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How to make the best use of graphics: Line graphs

Things you should know about Journals...

To support you in this, we've prepared a number of articles to assist you in making the right journal selection for your publication. If you would like a broad overview, start with our comprehensive article 'Navigating the Journal Selection & Submission Process', or jump in to one of these other related topics and get the information you need to be successful!
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How to make the best use of graphics: Line graphs

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