I'm using [ENSO dataset][1] from the NIST Statistical Reference Datasets as a test for nonlinear regression code. 
The data are monthly averaged atmospheric pressure differences between Easter Island and Darwin, called [Southern Oscillation][2] Index (SOI). In the test, the data are fitted with three sine cycles ([like this][3]).

I got curious about the Southern Oscillations and I started looking for more SOI data. I learned that there are a few different methods of how to calculate the SOI, but none of the other sources that I found (e.g. [here][4]) gives the same numbers are in the NIST StRD.

There is a reference in the dataset, _Numerical Methods and Software_ by Kahaner, Moler and Nash, where I found only that the data are for years 1962-1975.
So my question is not really about statistics: how the ENSO dataset is related to the SOI data from other sources.



  [1]: http://www.itl.nist.gov/div898/strd/nls/data/LINKS/DATA/ENSO.dat
  [2]: http://en.wikipedia.org/wiki/El_Ni%C3%B1o-Southern_Oscillation
  [3]: http://fityk.nieto.pl/_images/fityk-1.0.1-osx-so.png
  [4]: http://www.bom.gov.au/climate/current/soihtm1.shtml