Logarithmic scales

Logarithmic Scales

Logarithmic scales are scales that increase logarithmically in powers of 10; eg 0.1, 1, 10, 100 or 0.5, 5, 50, 500 etc. A graph can be log-log, where both axis use logarithmic scales, or log-normal/semi-log, where one axis is logarithmic and the other is normal.

Logarithmic scales are useful for showing a wide range of data on the same graph, which allows comparisons to be made. Logarithmic scales can only be used on line graphs, and are very useful for comparative line graphs where the values of different lines are very different. For example total world population can be plotted on the same graph as the population of Oceania when using logarithmic scales, this allows useful comparisons. They are also very useful for showing rates of change, with a steeper line indicated a faster rate of change in the variable being measured.

However care must be taken when reading values from log graphs as it is easy to make mistakes. These scales can also make data values that are widely different seem similar because they appear close to eachother on the graph. Further disadvatages of the use of these scales is the fact that 0 cannot be plotted; they also place a greater emphasis on smaller values because they give them a larger area on the graph.

Logarithmic scales are very useful in many ways, but their use remains very limited. The introduction of a logarithmic scale to any graph alters the shape of the graph dramatically.