The function converts a given string into a numeric value by concatenating its numerical digits.
[CODE]:
```python
def f(x):
    # Initialize an empty string to store the numerical digits
    numeric_value = ""

    # Iterate over each character in the input string
    for char in x:
        # Check if the character is a numerical digit
        if char.isdigit():
            # Append the digit to the numeric value string
            numeric_value += char

    # Convert the numeric value string to an integer and return it
    return int(numeric_value)
```

This code approximation takes a string as input, iterates over each character, checks if it is a digit, and appends it to the numeric value string. Finally, it converts the numeric value string to an integer and returns it.