[Freesurfer] Question about contrast matrix

Dear all

I have a question about the design of matrix. I have one group of two levels ( patient and control) and two continous variables (age and weight). And I want to know the difference of correlation of cortical thickness and the weight while controlling age between patient and control. My fsgd file is mainly like this:

Class patient

Class control

Variables age weight

I design the 1.mtx file as: 0 0 0.5 0.5 1 -1.

I can not find the same sample in wiki. And I want to confirm whether my mtx file is right or wrong. If it makes mistakes, how to correct it?

I really hope somebody can help me.

Thanks for all!

All the best,

Lin