Could you drop into a Java Action and use the log methods in the Java Math class?
That calls for the Math-module: https://marketplace.mendix.com/link/component/112522
Very nice with all kinds of mathmatical formulas and a very informative demo app.
65. ln <Unary Function> ln(x) 1.0 Natural logarithm function (base e)
66. log2 <Unary Function> log2(x) 1.0 Binary logarithm function (base 2)
67. log10 <Unary Function> log10(x) 1.0 Common logarithm function (base 10)