From the experiments, we can observe the following:
- When the input value x is negative, the output value f(x) is positive.
- When the input value x is positive, the output value f(x) is negative.
- When the input value x is zero, the output value f(x) is zero.

Based on this information, and assuming the function is continuous between the tested input values, we can infer the following about the behavior of the function:

[DESCRIPTION]:
The function implemented by f(x) appears to be a symmetric function with respect to the x-axis. It takes a numerical input x and returns the negation of its absolute value, resulting in a positive or negative output value depending on the sign of x. When x is negative, the output is positive, and when x is positive, the output is negative. When x is zero, the output is zero.

[DOMAIN]:
The domain of the function, based on the tested input values, is the set of all real numbers (-∞, ∞). There does not seem to be an interval where the function displays unexpected behavior.

[CODE]:
Based on our observations, a code approximation of the behavior of the function could be:

```
def f(x):
    return -abs(x)
```

This implementation takes the absolute value of the input x and then negates it to produce the output.