The LOG1PX function
computes the log of 1 plus the argument. The LOG1PX function is mathematically
defined by the following equation, where –1 < x:

$\begin{array}{c}LOG1PX\left(x\right)=log(1+x)\hfill \end{array}$
When x is close to 0,

`LOG1PX(x)`

can be more accurate than

`LOG(1+x)`

.