Catch up on today's top five analyst upgrades with this list compiled by The Fly: 1. Walmart (WMT) upgraded to Buy from Hold at Argus with analyst Christopher Graja saying he believes an improving job market should help low-and-middle-income shoppers spend more. 2. Sprint (S) upgraded to Neutral from Underperform at Macquarie. 3. iRobot (IRBT) upgraded to Overweight from Neutral at Piper Jaffray with analyst Troy Jensen saying tracking data shows iRobot is experiencing "exceptionally strong demand in North America." 4. Diodes (DIOD) upgraded to Buy from Neutral at Longbow with analyst Shawn Harrison saying he expects rising demand, pricing, and Pericom growth to drive sales, gross margins, and earnings higher. 5. Texas Capital (TCBI) upgraded to Overweight from Neutral at Piper Jaffray with analyst Brett Rabatin saying he sees Texas Capital outperforming peers. This list is just a portion of The Fly's full analyst coverage. To see The Fly's full Street Research coverage, click here.