You could define a generic detect(obj, ...) that dispatches (using S3): detect.formula(fo, data) detect.data.frame(data) detect.default(x, y, trial)
where the first two call the third thereby modeling it on lm, a common approach, and giving the user choice in interface. On Tue, May 12, 2009 at 6:18 AM, Titus von der Malsburg <malsb...@gmail.com> wrote: > > Hi list, > > I have a function that detects saccadic eye movements in a time series > of eye positions sampled at a rate of 250Hz. This function needs > three vectors: x-coordinate, y-coordinate, trial-id. This information > is usually contained in a data frame that also has some other fields. > The names of the fields are not standardized. > >> head(eyemovements) > time x y trial > 51 880446504 53.18 375.73 1 > 52 880450686 53.20 375.79 1 > 53 880454885 53.35 376.14 1 > 54 880459060 53.92 376.39 1 > 55 880463239 54.14 376.52 1 > 56 880467426 54.46 376.74 1 > > There are now several possibilities for the signature of the function: > > 1. Passing the columns separately: > > detect(eyemovements$x, eyemovements$y, eyemovements$trial) > > or: > > with(eyemovements, > detect(x, y, trial)) > > 2. Passing the data frame plus the names of the fields: > > detect(eyemovements, "x", "y", "trial") > > 3. Passing the data frame plus a formula specifying the relevant > fields: > > detect(eyemovements, ~x+y|trial) > > 4. Passing a formula and getting the data from the environment: > > with(eyemovements, > detect(~x+y|trial)) > > I saw instances of all those variants (and others) in the wild. > > Is there a canonical way to tell a function which fields in a data > frame are relevant? What other alternatives are possible? What are > the pros and cons of the alternatives? > > Thanks, Titus > > ______________________________________________ > R-help@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. > ______________________________________________ R-help@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.
