The LN function returns the natural logarithm of a number.
The LN and EXP functions are inverse operations.

>>-LN--(--expression--)----------------------------------------><
- expression
- An expression that returns a value of any built-in numeric, character-string,
or graphic-string data type. A string argument is cast to double-precision
floating point before evaluating the function. For more information
about converting strings to double-precision floating point, see DOUBLE_PRECISION or DOUBLE. The value of the argument must
be greater than zero.
If the data type of the argument is DECFLOAT(n),
the result is DECFLOAT(n). Otherwise, the data type of the
result is double-precision floating point. If the argument can be
null, the result can be null; if the argument is null, the result
is the null value.
Note
Results involving
DECFLOAT special values: For decimal floating-point values the
special values are treated as follows:
- LN(NaN)
returns NaN. 1
- LN(-NaN)
returns NaN. 1
- LN(Infinity)
returns Infinity.
- LN(-Infinity)
returns NaN. 1.
- LN(sNaN)
and LN(-sNaN)
return a warning or error.
- LN(0) returns -Infinity.
- LN with a negative argument, including -Infinity, returns NaN. 1
