Bug 112549

Version:           1.1.0 (using KDE 3.4.0, compiled sources)
Compiler:          gcc version 3.4.3
OS:                SunOS (sun4u) release 5.8

I have been thinking about some of the still unresolved issues linked with working with only subsets of the complete vectors. There are various scenarii where one may need to do this, like in bug #86915 (operate only on visible parts of plots) or bug #110734 (mask some "invalid" datapoints). But I believe the overall idea is that there should be an easy way of "pruning" data. If we provide the ability to do that based on expressions for one or many vectors at once, then implementing a solution to bug #86915 would become easy (just generate the appropriate expression, and prune). Bug #110734 could also be handled that way (but I won't mark them as duplicate just now :-)).

To describe what I have in mind in a more precise way, I imagine changing the "Change data sample ranges" tool to "Change sample ranges/Prune", with radiobuttons to choose between "Sample ranges" and "Expression" (and possibly a third one "Visible points" for bug #86915). The workflow would be the following:
- the user calls up the tool from the menu
- if he wants to restrict data based on sample ranges/numbers, he does it the usual way
- if he wants to prune data based on some criterion (max deviation from the mean, or anything else) the he inputs that expression in a lineedit and the vector is reduced to only points for which the expression returns "true"
- now something very important: if he has highlighted more than one vector in the listbox on top, then vectors should all be made to be the same length (including interpolated to that after user confirmation) and points excluded from one vector should be excluded from the others as well. That way, you could easily restrict all vectors to a given time interval without having to find out what the corresponding sample numbers are for each vector (believe me, this can become tedious with different sampling times!): you just type something like "([TIME]>=10.0) && ([TIME] < 20.0)", hit OK and you're done !
- finally, if the user wants to restrict vectors to only the parts that are visible, he can check that option, and kst generates the right expression based on X/Y scales and vectors shown in all plots and applies it.