format
The format is:
Time-Series [1:91] from 1 to 91: 2.33 1.89 2.08 1.82 1.82 ...source
Jones, R.H. (1984). Fitting multivariate models to unequally spaced data. In Time Series Analysis of Irregularly Observed Data, pp. 158-188. E. Parzen, ed. Lecture Notes in Statistics, 25, New York: Springer-Verlag.