d3
Suggestion: add an angle property to d3.forceRadial() to define the forces in this angle
It's a ground truth that in Polar coordinate system we need (angle,radius) to determine a position of a point. When I use d3.forceRadial to add a radial force on nodes, I surmise it could be more applicable if an angle() function is added to d3.forceRadial to define a force on an angle of radial. I thought it derives naturally without which we need to use d3.lineRadial to tranform this problem to what d3.forceCenter can solve.
For example, I want to draw a graph as the following.
Each circle in the graph needs to be positioned just at the cover of an arc as if an magnet force existed.
Nice idea. See https://observablehq.com/@fil/forceangular for an implementation.
Thank you for your reply. Actually, I've learned a lot from your coding.
New iteration of the code. The things that I was not happy with in the first iteration were:
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the force did not have the correct dimension (should have been in pixels per iteration) ; it's fixed now by multiplying the tangent vector by the distance to the center.
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points that were almost at the opposite of their target angle were boosted too much, resulting in spectacular (but wrong) movements; fixed by using
hypot(1, tan(diff/2))instead of 1+tan^2.
In both cases the result is mathematically justified, so I think the code is final. I don't know if it should be included in d3-force or not.
If it is included, and we want to modify d3.forceRadial to take into account the angle, there's a difficulty with the order of arguments: forceRadial(r, x, y) can't be easily expanded to forceRadial(r, a, x, y).
However we could define forcePolar(r, a, x, y), and make syntactic sugar for forceRadial(r, x, y) and forceAngular(a, x, y).
I think these new forces are very useful for various scenarios. Thanks for putting them together @Fil!
In case they don't make it to d3-force would be nice to have them available as NPM modules for ease of reuse. We can also list them on d3-force-registry.
I've mixed them into forcePolar https://observablehq.com/@fil/forcepolar with syntactic sugar for forceRadial and forceAngular