Function arcTween

src/traces/indicator/plot.js:798–805

(arc, endAngle, newAngle)

// Returns a tween for a transition’s "d" attribute, transitioning any selected
// arcs from their current angle to the specified new angle.
function arcTween(arc, endAngle, newAngle) {
    return function() {
        var interp = interpolate(endAngle, newAngle);
        return function(t) {
            return arc.endAngle(interp(t))();
        };
    };
}

// mocks our axis
function mockAxis(gd, opts, zrange) {