Simulated data
| id | numeric | Twin-pair id |
| zyg | character | Zygosity (MZ or DZ) |
| twinnum | numeric | Twin number (1 or 2) |
| agemena | numeric | Age at menarche (or censoring) |
| status | logical | Censoring status (observed:=T,censored:=F) |
| bw | numeric | Birth weight |
| msmoke | numeric | Did mother smoke? (yes:=1,no:=0) |
data.frame
Simulated