# Use gather() to convert the dataset to long format
air.long <- gather(airquality, variable, value, -Month, -Day)
head(air.long)
# Note that the syntax used here indicates we wish to gather ALL the columns except "Month" and "Day"

# Then, use spread() to convert the dataset back to wide format
air.wide <- spread(air.long , variable, value) 
head(air.wide)