Using this dataframe, produce a plot of the methane data contained
therein versus time. The relevant columns in the file are labelled “average” and
“decimal”, containing average methane levels in ppb and the date in years, respectively.
Clearly label the content, a plot simply showing the defaults “average” and “decimal”
will be insufficient.
If you encounter difficulties it may help to inspect the content of the csv file or the
dataframe directly

Next, plot the five fitted polynomials obtained by both methods, over
the range of dates used for the fitting. What do you observe?