[rkward-devel] case selection

[Thomas Friedrichsmeier]

Hi,

On Thursday 08 December 2011, meik michalke wrote:
> as of now, in RKWard it's possible to select subsets of variables (columns)
> from a given data.frame. i was just wondering if it's also possible to
> select cases (rows) in a similar way, already? like a selector box
> offering the rownames/numbers. ideally, it would allow to specify a column
> (e.g. with case numbers) as an alternative, and if the column is a factor,
> list only the factor levels.

well, of course, it would already be possible to create e.g. an embeddable 
plugin for subsetting. Equip this with a varselector, which you can root to 
the data.frame in question, and you can easily implement selection of a key 
column.

So far, selection of names / numbers / levels (and why not arbitrary 
conditions?) would require some manual keyboard input. Still, I think it would 
be possible to provide pretty decent support for many common subsetting tasks, 
this way. In fact, for a number of use cases (e.g. selecting a numeric range, 
selecting all subject ids starting with a certain sub-string, etc.) manual 
keyboard input will be much more usable than visual selection.

Regarding widgets for visual selection of row names, numbers, or levels, there 
are two problems:
1) Esp. row names and numbers can be a very long list. Users should not be 
_required_ to use visual selection. (I.e. one more reason to start working on 
a manual input solution, already.)
2) Currently, it is not possible for a plugin to fetch a list of row names or 
levels from the backend. Admittedly, this is mostly due to somewhat 
ideological reasons. In the mid term, I do plan to allow plugins to fetch 
arbitrary info from the backend, interactively. However, this still needs a 
bit of thinking to arrive at a clean solution. Please don't expect anything 
soon.

Regards
Thomas
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