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bisector no longer supports two-argument (object, value) comparator #249
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So you're saying bisector() compare function no longer supports object, right? Even though this case is mentioned (for sort()) in #217 (comment)
I don’t follow. What are you trying to do?
briefly: I have array of objects d, and want to bisect by d.x
the objects happen to have the x,y values
I can create new array of all d.x values if needed, but the change broke my current compare function
There are a lot of tests of bisecting arrays of objects:
https://github.com/d3/d3-array/blob/main/test/bisector-test.js
How is your usage different? Can you share a minimal, complete, live example of how it is not doing what you expect, say as an Observable notebook?
see https://observablehq.com/@louking/d3-bisector-with-object-comparison-function
I'm not sure the best way to get observable to print like console.log() but the debugger brings you into where you can see the console.log()
the
compare1(x,x)causes the bisector to always return hiReacted by Mike BostockIf you pass an accessor rather than a comparator,
bisectX = d3.bisector(d => d.x).left
then it works as intended.
https://observablehq.com/d/468b832f4f688643
But, I think you’re right that this might be a bug for bisector’s weird comparator that takes different arguments. I need to investigate a little more.
- changed the title
[-]bisector compare of array of objects no longer works[/-][+]bisector no longer supports two-argument (object, value) comparator[/+]on Apr 8, 2022 Also, it works if you implement a “normal” (symmetric, non-weird) comparator:
bisectX = d3.bisector((a, b) => a.x - b.x).left
And then you pass in test values that have the same shape as the things you are bisecting, e.g.
bisectX(dataarr, {x: 2})
However, this approach deviates from the example given in the README, and also deviates from the more recommended pattern of using an accessor (whereby you pass in a search value equivalent to the accessor’s output, not its input). So, I think at a minimum we need to update some documentation here, but ideally we find a way to make this work.
If you pass an accessor rather than a comparator,
bisectX = d3.bisector(d => d.x).left
then it works as intended.
I don't think this works for me, because my actual comparator handles both ascending and descending arrays.
that.bisectX = d3.bisector(function (d, x) { if (that.xascending) { return d.x - x; } else { return x - d.x; } }).left;
In the meantime, to work with d3 7.4.2, I've created a parallel array with just the
xvalues, and changedd.xin the above function tod.Thanks for your support!
In the descending case, you could say
bisectX = d3.bisector(d => -d.x).leftand then pass -x as the search value. Or you can use the symmetric comparator as I described in the other comment. Here is the descending form:
bisectX = d3.bisector((a, b) => b.x - a.x).leftand then pass an object {x} to search.
So, to flesh out the example, you could use a symmetric comparator like so:
bisectX = d3.bisector(xascending ? (a, b) => a.x - b.x : (a, b) => b.x - a.x).left
And then say
bisectX(array, {x})
Or you could use an accessor like so:
bisectX = d3.bisector(xascending ? (d) => d.x : (d) => -d.x).left
And then say
bisectX(array, xascending ? x : -x)
Reacted by Lou King
It looks like 22cdb3f broke my compare function, which used an array of objects.
I see I can use array of values, but wanted to point out this breaking change.
My compare function was
The breaking change is at
d3-array/src/bisector.js
Line 16 in 14efbe0