A log-log plot represents observed units described by two variables, say x and y , as a scatter graph . In a log-log plot, the two axes display the logarithm of values of the variables, not the values themselves.
If the relationship between x and y is described by a power law,
then the (x,y) points on the log-log plot form a line with the slope equal to a .
Log-log plots are widely used to represent data that are expected to be scale-invariant (or "fractal") - because fractal data usually follow a power law.