The top axis emphasizes the fact the data are logs. In Figure 2, the value of each tick mark is double the value of the preceding one. That is a second reason that I prefer dot plots over bar charts for these data. I don’t like using lengths with logarithmic scales.

A bar chart is judged by the length of the bar. Dot plot of data of Figure 2 shown on a log scale with base of 10Ī dot plot is judged by its position along an axis in this case, the horizontal or x axis. While a base of ten is useful when the data range over several orders of magnitude, a base of two is useful when the data have a smaller range.įigure3. The common base for logarithmic scales is the base 10. The equation y = log b (x) means that y is the power or exponent that b is raised to in order to get x. The equation 2 4 = 16 can be rewritten as log 2 16 = 4 and pronounced 'log to the base 2 of 16 is 4.' It is helpful to remember that the log is the exponent, in this case, '4'. To refresh your memory of school math, logs are just another way of writing exponential equations, one that allows you to separate the exponent on one side of the equation. Then I will provide more detail about each of these reasons and give examples. First I will review what we mean by logarithms. The second is to show percent change or multiplicative factors. The first is to respond to skewness towards large values i.e., cases in which one or a few points are much larger than the bulk of the data. There are two main reasons to use logarithmic scales in charts and graphs.

Log base 2 graph