format
The format is:
'ts' int [1:396, 1] 160218 143539 148158 139589 147395 161244 173733 177365 156875 154197 ...
- attr(*, "dimnames")=List of 2
..$ : NULL
..$ : chr "electricity"
- attr(*, "tsp")= num [1:3] 1973 2006 12source
Source: www.eia.doe.gov/emeu/mer/elect.html