Goldman Sachs analyst Jason English upgraded Kellogg Co. shares to buy from neutral late on Thursday, writing that he expects margin improvement and an acceleration in organic sales from the maker of cereals and snacks. The stock represents the "most compelling value left in snacks," in English's view, as the company shifts its main focus toward snack foods and away from cereal. The company has "invested behind faster-growing single serve snacks which resonate with consumer mega trends of portion control," English wrote. He raised his price target to $72 from $58. Kellogg shares are up 2% in Friday morning trading, and they've risen 12.5% on the year as the S&P 500 has gained 19%.