Exercise

Please use regular expression to answer the following:

• How can you get rid of ALL characters after the "@" symbol in c("wtl2109@columbia.edu is my email", "n0t_rea1_account@yahoo.com")?
• How can you erase the zip code from the following address c("1255 Amsterdam Ave New York, NY 10027", "612 W 115th St #715 New York, NY 10025") with regular expression?
• How can you replace all words that start with capital letter with an empty string c("Harry Ng works at Walgreens", "Larry Saltz is his name")?
• Repeat all the examples in the teaching section but replace everything with gsub() instead of sub() and guess the outcome before running the code.