RATINGS CHANGES

American Airlines (AAL) - Get Report was upgraded to buy at TheStreet Ratings. You can view the full analysis from the report here: AAL.

Amsurg (AMSG) was upgraded to outperform from market perform at Wells Fargo. The valuation is more attractive, with the stock down 24% since June, Wells said. 

Cabot Oil & Gas (CBT) - Get Report was downgraded to hold at TheStreet Ratings. You can view the full analysis from the report here: CBT.

Cornerstone (CSOD) - Get Report was downgraded to neutral from overweight at JPMorgan. $40 price target. The valuation is less attractive, as the stock has outperformed by 28% over the past two years, JPMorgan said. 

Tableau Software (DATA) - Get Report was downgraded to market perform at William Blair. The company lacks visibility and offered disappointing guidance, William Blair said. 

Envision (EVHC) was upgraded to outperform from market perform at Wells Fargo. The valuation is more attractive, Wells said. 

Frontier (FTR) - Get Report was downgraded to hold from buy at Deutsche Bank. $4 price target. The company can't cut costs fast enough to offset lower revenue, Deutsche said. 

Nucor (NUE) - Get Report was upgraded to buy from hold at Berenberg. $57 price target. The company is leveraged to higher steel prices, Berenberg said. 

Paycom (PAYC) - Get Report was downgraded to neutral from overweight at JPMorgan. $53 price target. The valuation is less attractive, as the stock has tripled in the past two years, JPMorgan said. 

Pfizer (PFE) - Get Report was downgraded to market perform from outperform at BMO Capital. The valuation is less attractive, based on a $33 price target, BMO said. 

Plantronics (PLT) - Get Report was downgraded to neutral from overweight at JPMorgan. $55 price target. Following mixed quarterly results, there appears to be better upside potential elsewhere, JPMorgan said. 

Square (SQ) - Get Report was upgraded to outperform from neutral at Credit Suisse. $15 price target. The company is seeing better growth and leverage, Credit Suisse said. 

This article was written by a staff member of TheStreet.