[R] Best Programming Practices regarding data frames

[Jeff Newmiller]

I think the vector is far more fundamental than the data frame. Most of the time I write functions that return vectors, even if my input is a data frame. If I need a large number of input vectors, I set up the input arguments to include a data frame and additional named parameters with defaults for the column names I will use. In the function I refer to the input columns using list indexing by name (D[[somecolname]]). In the rare event that I return a data frame, it has to include the appropriate "key columns" from the original, and will usually have the minimum number of input columns, and all columns have new, fixed (renamed) column names. (This usually is associated with the instantiation of a class I have defined.)

The use of vectors in function returns allows the caller to manage which columns make sense for the analysis at hand by tacking on new ones to the input data frame.
---------------------------------------------------------------------------
Jeff Newmiller                        The     .....       .....  Go Live...
DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live Go...
                                      Live:   OO#.. Dead: OO#..  Playing
Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
/Software/Embedded Controllers)               .OO#.       .OO#.  rocks...1k
--------------------------------------------------------------------------- 
Sent from my phone. Please excuse my brevity.

Ramiro Barrantes <ramiro at precisionbioassay.com> wrote:

>Hello,
>
>I come from using different programming languages (C++, Mathematica,
>Perl) but have been using R extensively for several months.  I see the
>data frame as a key piece of the language and wanted to inquire
>people's experience regarding its use.
>
>Say you have a data frame D
>
>D <- data.frame(some columns)
>
>and you define a function that needs the information from this data
>frame and is supposed to return a calculation based on some columns of
>such data frame D.
>
>func <- function(d) {}
>#EFFECT: Does calculation X from some columns of d
>
>QUESTION: Would you consider better practice to return the same
>data.frame but expanded, or would you return a small data frame that
>consists of the newly computed columns?
>
>Some might say, either way, personal preference.  But after using and
>seeing other's code for some time, I am thinking that returning the
>result that consists of ONLY the relevant columns is a better practice
>as it defines the function as only returning what it was intended to
>return, and leaves it up to the user of the function to do whatever
>they were intending to do with it (including naming of the new columns,
>adding them to a data frame, etc.).  This might be a question for a
>computer programming theory group, but if anybody has any insight from
>their experience please share.
>
>Thanks in advance,
>
>Ramiro
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help at r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.