You are given a function named calculate$\_$area$\_$circle intended to calculate the area of a circle. However, the function seems to have some errors. Your task is to debug the function step by step and make the necessary modifications to ensure it calculates the area correctly.

Start by running the function calculate$\_$area$\_$circle with some sample inputs and observe the output. Identify any errors or unexpected behavior.

Debug the code of the calculate$\_$area$\_$circle function line by line. Look for potential sources of error such as typos, incorrect variable names, or mathematical errors.

After making modifications to the function, test it again with various input values to ensure that it produces the expected output for a range of scenarios.

Add comments and documentation to the function code to explain its calculate$\_$area$\_$circle $<-$ function$($radius$)\{$

# Incorrect formula: area $=$ pi $*$ radius $($missing exponent$)$

area $<-$ pi $*$ radius

# Missing return statement

print$($area$)$ # Extra print statement

$\}$

calculate$\_$area$\_$circle$(6)$ # the output is is not valid

# it should throw the following warning messages when the function is used with undesirable arguments.

calculate$\_$area$\_$circle$(0)$ # Radius should be a non$-$zero numeric value.

calculate$\_$area$\_$circle$(-1)$ # Radius cannot be negative.

# calculate$\_$area$\_$circle$(3,4)$ # Radius should be a single value.

# calculate$\_$area$\_$circle$("$three$")$ # it should produce warning message: "Only numeric values are allowed"

# the above two lines $66$ and $67$ should be kept in comments while knitting, or else it will throw error while knitting to word

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