 U.S. stocks struggled for direction at the open on Tuesday, as investors weighed earnings from Goldman Sachs Group Inc. and Morgan Stanley as trading resumed following a three-day weekend honoring Martin Luther King Jr. The Dow Jones Industrial Average DJIA, -0.30 was down 0.2 soon after the opening bell, while the SP 500 SPX, -0.06 edged up 0.1 and the Nasdaq Composite COMP, -0.15 was trading about flat, according to FactSet data, at last check. Goldman Sachs and Morgan Stanley on Tuesday reported their results for the fourth quarter, with Goldman GS, -2.29 missing earnings estimates while Morgan Stanley MS, 4.72 beat analysts forecasts. 