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| − | \subsection{Functions in \textsf{R}}
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| − | In this lab the function objects were already introduced, and some basic
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| − | functions were applied. That was the case of the {\tt c()} function
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| − | which concatenates several elements in a vector, the {\tt matrix()}
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| − | function which transforms a vector in a matrix, the {\tt which()}
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| − | function which reports the elements where a given logical prove is TRUE,
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| − | etc..
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| − | Functions in \textsf{R} are very easy to apply because the programming
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| − | is the same in all cases. Applying a function is as easy as to type the
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| − | name of the function immediately followed (without space) by circular
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| − | brackets. Inside the circular brackets, the arguments of the function
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| − | are specified. A imaginary function named {\tt ResourcesAssessment()}
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| − | could be applied by using the following code:
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| − | <<eval=FALSE>>=
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| − | ResourcesAssessment(Arg_1, Arg_2, ..., Arg_i, ..., Arg_n)
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| − | @
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| − | where {\tt Arg\_i} are the n arguments which defineing the function
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| − | options.
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| − |
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| − | Not all arguments must be specified to apply the function, as some
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| − | arguments have default settings that are applied in the case that the
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| − | argument is not specified. Some arguments requires a single element to
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| − | be entered, but also vectors or even matrices, dataframes or other type
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| − | of objects can be arguments in a function, as shown above. Most of the
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| − | cases the argument must be entered by using its name. For instance, the
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| − | argument {\tt add=TRUE} controls in some graphical functions whether the
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| − | current plot is produced in a new chart or incorporated to the previous one.
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| − |
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| − | A question that may arise at this point is the list of the available
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| − | functions in \textsf{R}, or even the total number of it. It is a
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| − | difficult question to answer, as the number of functions is continuously
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| − | increasing. There is a set of functions included with the basic
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| − | \textsf{R} software (core), but the number of functions can be increased
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| − | by installing new packages. New packages can be downloaded from the URL
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| − | address of \textsf{R}, or being installed directly from \textsf{RStudio}
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| − | in the "Packages" tab of the Graphical output window. Even though it is
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| − | enough with installing once the new packages, packages not included in
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| − | the core must be activated each time to be used in a new \textsf{R}
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| − | session by using the {\tt library()} function.
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| − |
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| − | Even though the number of available functions is huge, should we be
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| − | interested in create a new one. It can be easily done in \textsf{R} but
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| − | it is far of the scope of this introductory lab.
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