gfilter: head/tail/some(..., 1000) preset

[landroni]

This is sitting rather high on my TODO list ( https://github.com/landroni/gWidgets2-filter/blob/master/TODO ), but I have trouble deciding how best to integrate it into gfilter().

I was thinking of providing a "preset" filtering item that could be 'Add'ed as other row filters, but instead of focusing on any given variable, it would present a generic interface for head(), tail() and car::some(). The funs are extremely useful when inspecting a data frame, for example when checking that some operation on a DF went as expected.

This thingy could take the form of a gfilterpreset() fun modeled on gfilter(), that when called via 'Add preset' would add a widget that has three radio choices c('head', 'tail', 'some'), with 'some' being disabled if package 'car' is not available and below either a scrollbar with 1:nrow(df) or a spinner with same range. I think it should be possible to checkbox negative for the range, as head and tail allow, but not some.

Is this feasible?

[landroni]

Oh, by default dffilter() would load this preset with head(..., 1000), as rstudio::View() does. I think it's useful, and if the user wants something else, they can remove the preset or change the subset value/function.

[jverzani]

I don't see why you couldn't do this. It might be better to parse some input for the lines, e,g,:

1:10, 11, 15:22

Since you are parsing, you could even have an end (julia like, with 1:end) instead of 1:length(x) (but x is not really a variable so that would be confusing).

[landroni]

I now came up with a working prototype of the feature. Several implementation issues persist:

• For the life of me I cannot set the default slider value to 1001. In standalone code sl <- gslider(from=1, to=1645, value=1001, by=10, cont=g, expand=TRUE, fill="both") this works fine, but it refuses to work in gfilter()? Any ideas why?
• Is it possible to specify instead of by= a vector with all the steps that the slider should have? For example, for a dataframe with 103 rows, I'd like to have as steps: 10, 20, ..., 90, 100, 103. As it is I'm not sure that this can be done.
• The 'generic' preset implementation is not sufficiently polished, so it's disabled in the code.
• How is it possible to completely disable (make in-visible) the "include NA" checkbox? I tried PresetItem$new(x, name=name, parent=.self, includeNA=FALSE), but this doesn't seem the right way to go about it.

[landroni]

All the issues noted above have been addressed one way or another in the updated PR. Now the feature is pretty much complete and ready for inclusion.