implement _estimateSigmaR2 etc. in diskdf for speedy estimate of sigmaR2
implement _estimateSigmaR2 etc. in diskdf for speedy estimate of sigmaR2

followthesheep/galpy,followthesheep/galpy,followthesheep/galpy,jobovy/galpy,jobovy/galpy,followthesheep/galpy,jobovy/galpy,jobovy/galpy