public function getMostPurCategory()
    {
        $categories = '';
        $productId = $this->model->getProductIdForMostSoldProduct();
        //sales data found for customer with product id
        if ($productId) {
            $product = $this->getProduct($productId);
            //product found
            if ($product->getId()) {
                $categoryIds = $product->getCategoryIds();
                if (count($categoryIds)) {
                    $categories = $this->getCategoryNames($categoryIds);
                }
            }
        }

        return $categories;
    }