format
The data set is a zoo series with a "Date" class time index
and 6 numeric numeric columns.
ll{
start date of start of billing period
therms integer number of therms used in this billing period
gas Total cost of gas (including delivery and commodity charges) for
natural gas
KWHs integer number of KWH used in this billing period
elect Total cost of electricity (including delivery and commodity
charges)
temp average daily outdoor temperature in degrees Fahrenheit, as
printed on the bill
days number of days in billing period.
}source
Zembower, Kevin,
https://www.stat.math.ethz.ch/pipermail/r-help/2006-October/115499.html and correction of one documentation item in https://www.stat.math.ethz.ch/pipermail/r-help/2006-October/115632.html.