Modern R Programming Cookbook

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Any function in R with either a single argument or multiple arguments works similarly. The only difference is the internal calculation and the use of arguments. In this function, the type argument takes only two values, but there is no way to check the input. For example, if someone mistakenly wrote type = "Robust", then the function will not provide any output. R is case sensitive, so robust and Robust are treated very differently.

To handle this ambiguity, you can write a few extra statements within the function body. The extra statement is to convert the type input into either all lowercase or all uppercase so that it works for both Robust and robust. Following are the lines of code that are needed in the body of the function ...