The function f(x) maps input strings to their corresponding numeric representations.

[CODE]:
```
def f(x):
    numerical_mapping = {
        "input1": "one",
        "input2": "two",
        "input3": "three"
    }
    return numerical_mapping.get(x, "unknown")
```

This code assumes that the function f(x) has a predefined mapping between input strings and their corresponding numeric representations. The `numerical_mapping` dictionary stores these mappings, and the function returns the corresponding value for a given input string. If the input string is not found in the dictionary, the function returns "unknown" as a default value.

Please let me know if you need further assistance or if there's anything else I can help you with.