difference mark and shift transform #1896
Conversation
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Now improved! I have an open question as to whether this should support the z channel, and what to do if fill, fillOpacity, stroke, strokeOpacity, or strokeWidth are specified as channels. I’m inclined to say that these are not supported (at least for now — I’m trying to keep things simple). But I also don’t protect against them, and I’m not entirely sure how we would protect against them. What do you think? Perhaps this elucidates why I think requests like #175 would be so difficult to support! |
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Toyed with this in #1897 in a composite mark; I also worked on the default tip contents, to show y1, y2, and the actual difference = y1-y2 (which is the point of this mark). I'd like to suggest two changes to the options, for a bit more consistency:
this way opacity would be the usual overall mark opacity (line + areas), strokeOpacity would be used on the line. |
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For the record, this (correctly) ignores the computed difference value from the default tip which I suggested in #1897. It was in fact a wrong good idea, because the difference mark is showing the visual difference between scaled values, which is not necessarily encoding y2 − y1. (Adding the difference to the default tip would have been correct only if we could assume a linear scale for y.) Users can add it explicitly with the channels option, e.g.:
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…**positive**, **negative** are the fill colors for their respective difference areas
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LGTY @Fil? |
* difference mark * fix filtering; opacity options * remove unused import * withTip; don’t duplicate channels * difference as a composite mark * difference tip * reuse channels * more composite marks * apply clip as render transform * consolidate code * aria labels * organize imports * fix differenceY1 test * update tests * better defaults * handle ChannelValueSpec * update test * memoTuple * checkpoint docs * fix differenceY1 test * tip fixes * **positiveOpacity**, **negativeOpacity** default to **fillOpacity**; **positive**, **negative** are the fill colors for their respective difference areas * positiveFill * another test * positiveFillOpacity & fix test * swap [xy][12]; default y1 = 0 * shift option * another difference example * z * simpler marks (no need for two differences) * inferScaleOrder * simpler chart * enhanced group extent; findX sketch * shift transform * shift domain hint * promote stroke to z * simpler channel domain hint * more difference docs * more difference docs * more documentation * call next twice (once for the path, once for the clipPath) * support clip: frame * document differenceY * test ordinal difference * adopt Plot.find * more docs --------- Co-authored-by: Philippe Rivière <fil@rezo.net>
Fixes #159. Fixes #1799. TODO:
differenceX?shiftY transform?