make reversed-radial-axis hover logic more readable

Author: etpinard

src/traces/barpolar/hover.js

@@ -26,15 +26,14 @@ module.exports = function hoverPoints(pointData, xval, yval) {
     var maxHoverDistance = pointData.maxHoverDistance;
     var period = angularAxis._period || 2 * Math.PI;
 
+    var rVal = Math.abs(radialAxis.g2p(Math.sqrt(xval * xval + yval * yval)));
+    var thetaVal = Math.atan2(yval, xval);
+
     // polar.(x|y)axis.p2c doesn't get the reversed radial axis range case right
     if(radialAxis.range[0] > radialAxis.range[1]) {
-        xval *= -1;
-        yval *= -1;
+        thetaVal += Math.PI;
     }
 
-    var rVal = Math.abs(radialAxis.g2p(Math.sqrt(xval * xval + yval * yval)));
-    var thetaVal = Math.atan2(yval, xval);
-
     var distFn = function(di) {
         if(inboxFn(rVal, thetaVal, [di.rp0, di.rp1], [di.thetag0, di.thetag1], vangles)) {
             return maxHoverDistance +