How do I rescale a geometry instance in an InstanceMesh?

I have an app with many many instances of an identically shaped and scale object so I am using THREE.InstancedMesh. It works fine.

Here is the code:

function doStuff() {

    // canonical ball geometry
    const geometry = new THREE.SphereBufferGeometry(1, 32, 16);

    const mesh = new THREE.InstancedMesh(geometry, material, vertices.length);

    // position and scale each ball instance
    const ballProxy = new THREE.Object3D()
    vertices.forEach((vertex, i) => {

        const { x, y, z } = vertex
        ballProxy.position.set(x, y, z)

        ballProxy.scale.setScalar(ballRadius)

        ballProxy.updateMatrix()

        mesh.setMatrixAt(i++, ballProxy.matrix)
    });

    return mesh
}

I now need to be able to interactively adjust the ball radii to a larger of smaller value. All instances will have the identical value. I am unclear on how to go about this.

I’m not sure if setScalar method exist, I think it should be object.scale.set(x, y, z)

Actually, the code snippet works fine. What I need is the ability to interactively - increment/decrement - the radius of all balls to the same value.