Semilog graph

In science and engineering, a semi-log graph or semi-log plot is a way of visualizing data that are changing with an exponential relationship. One axis is plotted on a logarithmic scale. All functions of the form $y=lambda\; a^\{gamma\; x\}$ form straight lines, since taking logs of both sides is equal to

:$log\_a\; y\; =\; gamma\; x\; +\; log\_a\; lambda$

This can easily be seen as a line in slope-intercept form with $gamma$ as slope, $log\_a\; lambda$ as the y-intercept. To facilitate use with logarithmic tables, one usually takes logs to base 10 or e:

:$log\; (y)\; =\; (gamma\; log\; (a))\; x\; +\; log\; (lambda)$

The term log-lin is used to describe a semi-log plot with a logarithmic scale on the y axis, and a linear scale on the x axis. Likewise, a lin-log graph uses a logarithmic scale on the x axis, and a linear scale on the y axis.

A log-log graph uses the logarithmic scale for both axes, and hence is not a semi-log graph.

ee also

* log-log graph