The format is:
num [1:43824, 1:12] 2010 2010 2010 2010 2010 2010 2010 2010 2010 2010 ...
- attr(*, "dimnames")=List of 2
..$ : chr [1:43824] "1" "2" "3" "4" ...
..$ : chr [1:12] "year" "month" "day" "hour" ...
Details
It records 43824 daily measurements on 12 variables and there are 2067 missing values on 2067 measurements, accounting for 0.00393.
References
X. Liang, T. Zou, B. Guo, S. Li, H. Zhang, S. Zhang, H. Huang, and S. Chen. Assessing Beijing's PM2.5 pollution: severity, weather impact, APEC and winter heating. Proceedings of the Royal Society A, 471(2182):1–20, 2015.