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Add center.strength.

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Fixes #81.
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Mike Bostock 2020-08-12 14:16:18 -07:00
parent 88e57e2593
commit c46be8de85
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2 changed files with 13 additions and 5 deletions
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10
README.md
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@ -179,18 +179,22 @@ Assigns the array of *nodes* to this force. This method is called when a force i
The centering force translates nodes uniformly so that the mean position of all nodes (the center of mass if all nodes have equal weight) is at the given position ⟨[*x*](#center_x),[*y*](#center_y)⟩. This force modifies the positions of nodes on each application; it does not modify velocities, as doing so would typically cause the nodes to overshoot and oscillate around the desired center. This force helps keeps nodes in the center of the viewport, and unlike the [positioning force](#positioning), it does not distort their relative positions.
<a name="forceCenter" href="#forceCenter">#</a> d3.<b>forceCenter</b>([<i>x</i>, <i>y</i>]) [<>](https://github.com/d3/d3-force/blob/master/src/center.js#L1 "Source")
<a name="forceCenter" href="#forceCenter">#</a> d3.<b>forceCenter</b>([<i>x</i>, <i>y</i>]) [<>](https://github.com/d3/d3-force/blob/master/src/center.js "Source")
Creates a new centering force with the specified [*x*-](#center_x) and [*y*-](#center_y) coordinates. If *x* and *y* are not specified, they default to ⟨0,0⟩.
<a name="center_x" href="#center_x">#</a> <i>center</i>.<b>x</b>([<i>x</i>]) [<>](https://github.com/d3/d3-force/blob/master/src/center.js#L27 "Source")
<a name="center_x" href="#center_x">#</a> <i>center</i>.<b>x</b>([<i>x</i>]) [<>](https://github.com/d3/d3-force/blob/master/src/center.js "Source")
If *x* is specified, sets the *x*-coordinate of the centering position to the specified number and returns this force. If *x* is not specified, returns the current *x*-coordinate, which defaults to zero.
<a name="center_y" href="#center_y">#</a> <i>center</i>.<b>y</b>([<i>y</i>]) [<>](https://github.com/d3/d3-force/blob/master/src/center.js#L31 "Source")
<a name="center_y" href="#center_y">#</a> <i>center</i>.<b>y</b>([<i>y</i>]) [<>](https://github.com/d3/d3-force/blob/master/src/center.js "Source")
If *y* is specified, sets the *y*-coordinate of the centering position to the specified number and returns this force. If *y* is not specified, returns the current *y*-coordinate, which defaults to zero.
<a name="center_strength" href="#center_strength">#</a> <i>center</i>.<b>strength</b>([<i>strength</i>]) · [<>](https://github.com/d3/d3-force/blob/master/src/center.js "Source")
If *strength* is specified, sets the centering force’s strength. A reduced strength of e.g. 0.05 softens the movements on interactive graphs in which new nodes enter or exit the graph. If *strength* is not specified, returns the force’s current strength, which defaults to 1.
#### Collision
The collision force treats nodes as circles with a given [radius](#collide_radius), rather than points, and prevents nodes from overlapping. More formally, two nodes *a* and *b* are separated so that the distance between *a* and *b* is at least *radius*(*a*) + *radius*(*b*). To reduce jitter, this is by default a “soft” constraint with a configurable [strength](#collide_strength) and [iteration count](#collide_iterations).

8
src/center.js
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@ -1,5 +1,5 @@
export default function(x, y) {
var nodes;
var nodes, strength = 1;
if (x == null) x = 0;
if (y == null) y = 0;
@ -15,7 +15,7 @@ export default function(x, y) {
node = nodes[i], sx += node.x, sy += node.y;
}
for (sx = sx / n - x, sy = sy / n - y, i = 0; i < n; ++i) {
for (sx = (sx / n - x) * strength, sy = (sy / n - y) * strength, i = 0; i < n; ++i) {
node = nodes[i], node.x -= sx, node.y -= sy;
}
}
@ -32,5 +32,9 @@ export default function(x, y) {
return arguments.length ? (y = +_, force) : y;
};
force.strength = function(_) {
return arguments.length ? (strength = +_, force) : strength;
};
return force;
}