The format is:
int [1:226400, 1:7] 1217951746 1217951836 1217951926 1217952016 1217952106 1217952196 1217952286 1217952376 1217952466 1217952556 ...
- attr(*, "dimnames")=List of 2
..$ : NULL
..$ : chr [1:7] "date_as_sec" "lat" "lon" "t_intervals" ...