Dear Douglas and Trisanna,
Thank you very much for your explanations.
I just would like to be sure of what I am doing since there is no example on the wiki as complex as mine.
If I have the following classes :
Diagnosis : Patient or Control
Gender : Male or Female
Site : Site1 or Site2 or Site3
NregressorsDODS = Nclasses*(Nvariables+1) = 6*(0+1) = 2*2*3*(1+1) = 24
Regressor1: ones for PatientMaleSite1 subjects, 0 otherwise. Codes intercept for Group 1
Regressor2: ones for PatientMaleSite2 subjects, 0 otherwise. Codes intercept for Group 2
Regressor2: ones for PatientMaleSite3 subjects, 0 otherwise. Codes intercept for Group 3
....
Regressor12: ones for ControlFemaleSite3 subjects, 0 otherwise. Codes intercept for Group 12
Regressor13: age for PatientMaleSite1 subjects, 0 otherwise. Codes age slope for Group 1
Regressor14: age for PatientMaleSite2 subjects, 0 otherwise. Codes age slope for Group 2
...
Regressor24: age for ControlFemaleSite3 subjects, 0 otherwise. Codes age slope for Group 12
I assume my FSGDF file should look like :
GroupDescriptorFile 1
Title analysis
Class PatientMaleSite1
Class PatientMaleSite2
Class PatientMaleSite3
Class PatientFemaleSite1
Class PatientFemaleSite2
Class PatientFemaleSite3
Class ControlMaleSite1
Class ControlMaleSite2
Class ControlMaleSite3
Class ControlFemaleSite1
Class ControlFemaleSite2
Class ControlFemaleSite3
Variables Age
Input subject1 PatientMaleSite1 30
Input subject2 PatientFemaleSite2 45
Input subject3 PatientFemaleSite3 85
Input subject4 PatientFemaleSite4 75
...
As for the contrast analysis :
If my question is : is there a difference between Patient and Controls age slope regressing out the effects of gender and site?
Contrast1 patient-control.slope.mtx
0 0 0 0 0 0 0 0 0 0 0 0 0.5 0.5 0.5 0.5 0.5 0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5
with all regressor1 to regressor12 equal to 0
with regressor13 to 18 equal to 0.5 (regressor with Patient in it)
with regressor19 to 24 equal to - 0.5 (regressor with Controls in it)
If my question is : is there a difference between cortical thickness in patients and controls, regressing out the effects of age, gender and site ?
Contrast2 patient-controls.mtx
0.5 0.5 0.5 0.5 0.5 0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 0 0 0 0 0 0 0 0 0 0 0 0
with all regressor1 to regressor6 equal to 0.5
with all regressor7 to regressor12 equal to -0.5
with all regressor13 to regressor24 equal to 0
Thank you very much in advance for your help and sorry for taking your time.
Best,
Charles