def _calc_derived_fields(self, fields):
<EOL>temp = fields['<STR_LIT>']<EOL>hum = fields['<STR_LIT>']<EOL>wind = fields['<STR_LIT>']<EOL>wind10min = fields['<STR_LIT>']<EOL>fields['<STR_LIT>'] = calc_heat_index(temp, hum)<EOL>fields['<STR_LIT>'] = calc_wind_chill(temp, wind, wind10min)<EOL>fields['<STR_LIT>'] = calc_dewpoint(temp, hum)<EOL>now = time.localtime()<EOL>fields['<STR_LIT>'] = time.strftime("<STR_LIT>", now)<EOL>fields['<STR_LIT>'] = now[<NUM_LIT:0>]<EOL>fields['<STR_LIT>'] = str(now[<NUM_LIT:1>]).zfill(<NUM_LIT:2>)<EOL>now = time.gmtime()<EOL>fields['<STR_LIT>'] = time.strftime("<STR_LIT>", now)<EOL>fields['<STR_LIT>'] = now[<NUM_LIT:0>]<EOL>fields['<STR_LIT>'] = str(now[<NUM_LIT:1>]).zfill(<NUM_LIT:2>)<EOL>
calculates the derived fields (those fields that are calculated)