Linear Threshold Covariate Example
  Origin 2 !I
  Sire 6 !I
  Season 2 !I
  Pelvic_Opening
  Sex 2 !A
  Birth_Weight
  Diff 2 !A
  Score
linthresh.dat !ASUV !MAXIT 100
Score Pelvic_Opening !BINOMIAL !LOGIT ~ Trait Trait.Origin,
Trait.Season Trait.Sex at(Trait,1).Pelvic_Opening !r Trait.Sire
1 2 1
0 0 I
2 0 US 1 0 1100 !GPZP
Trait.Sire 2
2 0 US .4 -.1 100 !GP
6 0 I