The format is:
table [1:5, 1:2] 25 18 13 27 3 4 5 22 41 14
- attr(*, "dimnames")=List of 2
..$ Smoking_type: chr [1:5] "Extreme smoker" "Very heavy smoker" "Heavy smoker" "Moderate smoker" ...
..$ Group : chr [1:2] "Lung cancer" "Healthy control"
Details
Extreme smoker: 10-15 cigars, >35 cigarettes, or >50 g pipe tobacco/day.
Very heavy smoker: 7-9 cigars, 26-35 cigarettes, or 36-50 g pipe tobacco/day.
Heavy smoker: 4-6 cigars, 16-25 cigarettes, or 21-35 g pipe tobacco/day.
Moderate smoker: 1-3 cigars, 1-15 cigarettes, or 1-20 g pipe tobacco/day.
References
Richard Doll (1998), Uncovering the effects of smoking:
historical perspective. Statistical Methods in Medical Research,
7(87), 87-117