process_gas_df.jl

function process_gas_df(df_all_gas::DataFrame)

    df_gas = deepcopy(df_all_gas)

    # Temperature is 10x in original data
    df_gas[!, :T] = df_gas[!, :T] ./ 10

    # Convert from kWh to m^3
    conversion_factor = 0.10058
    df_gas[!, :ch] = df_gas[!, :ch] .* conversion_factor
    df_gas[!, :hw] = df_gas[!, :hw] .* conversion_factor

    # Convert to Date object
    df_gas[!, :d] = Date.(df_gas[!, :d], "dd-mm-yyyy")

    # Rename all colums
    rename!(df_gas, Dict(:T  => "OutsideTemperature", 
	                 :ch => "CentralHeating",
	                 :hw => "HotWater",		
	                 :d  => "Date"))

    # Get column with day names
    day = map(x -> Dates.dayname(x), df_gas[!, :Date])
    insertcols!(df_gas, ncol(df_gas), :Day => day)

    return df_gas

end