Editor's Note: TheStreet ratings do not represent the views of TheStreet's staff or its contributors. Ratings are established by computer based on metrics for performance (which includes growth, stock performance, efficiency and valuation) and risk ( volatility and solvency). Companies with poor cash flow or high debt levels tend to earn lower ratings in our model. NEW YORK ( TheStreet ) -- Piedmont Office Realty (NYSE: PDM ) has been upgraded by TheStreet Ratings from hold to buy. The company's strengths can be seen in multiple areas, such as its revenue growth, reasonable valuation levels and increase in stock price during the past year. We feel these strengths outweigh the fact that the company has had somewhat weak growth in earnings per share. Highlights from the ratings report include:. Piedmont Office Realty Trust, Inc. engages in the acquisition and ownership of commercial real estate properties in the United States.