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2016-03-13gas model: add proper He compressibility data and do a least-squares fitGravatar Linus Torvalds
Lubomir pointed to exactly where he got his data from, so I added that raw Helium data to the R script, and let the least-squares fit just take care of the interpolation between 273K and 323K. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
2016-03-13gas-model: add R compressibility scriptGravatar Linus Torvalds
It annoyed me that we hand-waved a bit about how the virial factors were actually computed in the gas-model.c file, so here's an actual R script that computes them and plots the results. You can run it with (for example): R --vanilla < compressibility.r and it will generate a Rplots.pdf of the plots, and the coefficients will be shown on stdout. The result actually differs in insignificant ways from the values that Lubomir computed, which is likely just due to tools. I used R, Lubomir seems to have used http://polynomialregression.drque.net/online.php but the actual curve is pretty much the same. NOTE! R is not entirely happy about the non-linear fit of the Helium curve: the fit is *so* precise that it failes the R relative-offset convergence criterion. That is apparently generally a sign of artificial data. That is probably because Lubomir generated them from the linear mix of two polynomial fits, rather than a linear mix of the original data. But maybe the original data was artificial? Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Dirk Hohndel <dirk@hohndel.org>