Principal component of current, former and never smokers using (A) the 161 tags deemed reversible upon smoking cessation (Additional file 6) and (B) the 152 tags deemed irreversible upon smoking cessation (Additional file 7). Expression values used were scaled to tags per million (TPM). Each tag was then normalized by dividing its value by the maximum value for that tag seen in all the libraries. Subsequently, this value was then multiplied by 6 and then subtracted by 3 to put the values in the range of -3 to 3. A co-variance based approach was used and the statistics toolbox in MatLab (Mathworks) was used. Current smokers are represented in red, former smokers are represented in blue and never smokers are represented in green.
Chari et al. BMC Genomics 2007 8:297 doi:10.1186/1471-2164-8-297