Table 3 
Classification rules 
Classification Rule 1 based on the intensities at the 7 M/Z values: 
Let 
a_{1 }= (1303,5.66302,5.48787.19.60743,8.88828,30.47983,0.34510)', 
a_{2 }= (1413,6.44028,6.36701,20.84677,11.04580,32.04436,0.03553)', 
c_{1 }= 2984, 
c_{2 }= 3521. 
Let X be the vector that represents the intensities from a subject at the 7 M/Z values: 
2.7921478, 245.53704, 261.8864, 418.1136, 435.0751, 464.3617, 4003.645. Classify X into the cancer group if 
(a_{1 } a_{2})' X + (c_{1 } c_{2}) ≥ 0; 
Otherwise classify X into the control group. 
Classification Rule 2 based on the intensities at the 13 M/Z values: 
Let 
a_{1 }= (24.58884,15.09887,0.95772,3.16411,10.93854,31.7966,8.11259,6.59602,53.15727, 7.49888,149.18784,399.67258,112.83481)', 
a_{2 }= (26.26343,19.06632,1.07975,1.89482,9.83188,29.47779,7.69470,8.54597,49.99409, 7.32192,142.08982,389.53254,116.55493)', 
c_{1 }= 1386, 
c_{2 }= 1312. 
Let X be the vector that represents the intensities from a subject at the following 13 M/Z values: 2665.397, 3969.469, 3991.844, 4003.645, 4027.3, 4056.967, 4744.889, 6801.495, 7756.437, 8349.266, 14796.14, 15955.47, 17034.05. 
Classify X into cancer if 
(a_{1 } a_{2})' X + (c_{1 }c_{2}) ≥ 0. 
Otherwise classify X into control. 
Classification rule #3 based on 7 M/Z values: 
Let 
a_{1 }= (6.04377,3.42186,1.99804,0.23374,2.46593,1.87559,17.37384)', 
a_{2 }= (7.35920,1.86527,1.32486,0.92386, 1.18336,4.76619,9.95349)', 
c_{1 }= 218.19592, 
c_{2 }= 254.33039. 
Let X be the column vector that represents the intensities from a subject at the following 7 M/Z values: 
418.1136, 435.0751, 464.3617,4003.645, 4906.962, 6599.823, 6801.495. 
Classify X into cancer if 
(a_{1 } a_{2})' X + (c_{1 } c_{2}) ≥ 0. 
Otherwise classify X into control. 

Sorace and Zhan BMC Bioinformatics 2003 4:24 doi:10.1186/14712105424 