Caption: An example of a log-log plot.

Features:

1. Logarithmic plots are where one or both axes are logarithmic. If both are, it is a log-log plot; if only one, it is a semi-log plot.

   You do NOT have to know what a logarithm is to appreciate log plots. In fact, you quickly develop an intuitive understanding of them.

2. Logarithmic plots are useful for showing a function over many orders of magnitude by allowing you to see the functional behavior on many scales simultaneously.

   The cost of logarithmic plots is that functions are a bit distorted by linear-scale standards. But, in fact, there is NOT much cost because you usually quickly develop an intuitive understanding of them.

3. Logarithmic plots achieve their many-scales effect by having tick marks the on axes separated by factors (usually powers of 10) of a quantity and NOT constant amounts of the quantity.

   In logarithmic plots jargon one power of 10 is called a dex.

4. To explicate further, on linear-scale plots, much of the behavior of a function that varies tremendously with scale (like the function in the image) is off the plot or is squashed down to the x-axis and/or y-axis.

   Many linear-scale plots may be needed to show the whole functional behavior in roughly equal detail.

5. For example for the function in the image, if you displayed the whole function on a linear-scale plot, all the lower left behavior would be squashed into the x-axis and y-axis, and would be invisible or nearly invisible.

   The log-log plot allows us to see that behavior easily.

Credit/Permission: © David Jeffery, 2004 / Own work.
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