Sorry- I did not carefully read Johns reply. I think he is saying that
without
a mat file, a matrix that is not identical to eye(4) is generated as a default
space. To get around this, lets call this matrix MM for "mystery matrix", and
we want to solve for M3 so that
MM * vc_2 = M3 * vc_1
The "mystery matrix" can be found with spm_get_space, which is in the recent
updates to spm2.
So, from before:
vc_2 = inv(M2) * M1 * vc_1
inv(MM) * MM * vc_2 = inv(M2) * M1 * vc_1
MM * vc_2 = inv(MM) * inv(M2) * M1 * vc_1
M3 = inv(MM) * inv(M2) * M1
Ken
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