code: function(o) {
              o = (o && point(o)) || point(0,0);
              var x = this.x;
              var y = this.y;
              this.x = sqrt((x-o.x)*(x-o.x) + (y-o.y)*(y-o.y));   // r
              this.y = toRad(o.theta(point(x,y)));
              return this;
          }
docs: Converts rectangular to polar coordinates. An origin can be specified, otherwise it's 0@0.