* Futures up: Dow 58 pts; S&P 3.25 pts; Nasdaq 13.5 pts (Adds details, comment, updates prices)
July 31 (Reuters) - U.S. stock indexes looked set to open higher on Monday as investors remained optimistic about corporate earnings in the second quarter and ahead of a clutch of economic data.
Investors have been counting on earnings to support the relatively high valuations for equities, with the S&P 500 trading at about 18 times earnings estimates for the next 12 months, above its long-term average of 15 times.
Of the 289 S&P 500 companies that reported results until Friday, 73 percent of them beat analyst expectations. This is above the 71 percent average over the past four quarters, according to Thomson Reuters I/B/E/S.
The S&P 500 slipped on Friday on negative reactions to earnings reports from high-profile names such as Amazon , Exxon and Starbucks and a drop in shares of tobacco companies.
"We had a choppy week last week, we had a very erratic week, so coming off a erratic week, we're getting some early morning premarket bargain hunting," said Andre Bakhos, managing director at Janlyn Capital LLC.
Apple Inc, a part of the Dow, is expected to report quarterly results after market close on Tuesday and its performance may hold the sway over tech stocks this week.
Data vying for attention includes ISM Chicago Purchasing Managers' Index data that is expected at 9:45 a.m. ET. The reading, which is an indicator of the strength of U.S. manufacturing sector, is likely to show a slight dip in July.
The Federal Reserve of Dallas will release its monthly manufacturing index for July at around 10:30 a.m. ET.
Oil prices rose on Monday, putting July was on track to become the strongest month for the commodity this year.
"What is causing the erratic behavior is a lack of the healthcare bill, any legislation coming from the Congress," Bakhos said.
"So right now, we're going to get some hesitation, hopefully until signs come out of Washington that things will be on the move."
The seven-year Republican quest to scrap Obamacare, a major campaign vow by President Donald Trump, lay in ruins last week after the Senate failed to dismantle the healthcare law.
Dow e-minis were up 58 points, or 0.27 percent, with 19,868 contracts changing hands at 8:20 a.m. ET (1220 GMT). S&P 500 e-minis were up 3.25 points, or 0.13 percent, with 132,207 contracts traded. Nasdaq 100 e-minis were up 13.5 points, or 0.23 percent, on volume of 26,173 contracts.
Scripps Network was up 1.23 percent at $87.98 premarket after Discovery Communications said it would buy the media company for $14.6 billion.
Charter Communications Inc up 8 percent after the U.S. cable operator said on Sunday it was not interested in buying wireless carrier Sprint Corp.
Shares of Snap Inc fell 3 percent in premarket trading as a share lockup ended, allowing for sales by early investors and pushing it further below its March initial public offering price. (Reporting by Ankur Banerjee, Sweta Singh, Sruthi Shankar and Yashaswini Swamynathan in Bengaluru; Editing by Arun Koyyur)