Question about contrast and margin

[Liang Wang Jack]

Dear scientist,

If I want to compare the mean of different variable levels between two groups, after fitting linear mixed model, what is the difference between using

contrast

and

margin

For example, my group variable has 2 levels (group A and group N); Mask variable has 3 levels (mask1, mask2, mask3); braintract has 3 levels (braintract1, braintract2, braintract3)

Compare FA values between two group

Group A v.s. Group N
Mask1braintract1 v.s. Mask1braintract1
Mask1braintract2 v.s. Mask1braintract2
Mask1braintract3 v.s. Mask1braintract3
Mask2braintract1 v.s. Mask2braintract1
Mask2braintract2 v.s. Mask2braintract2
Mask2braintract3 v.s. Mask2braintract3
Mask3braintract1 v.s. Mask3braintract1
Mask3braintract2 v.s. Mask3braintract2
Mask3braintract3 v.s. Mask3braintract3

With this linear mixed model (mask nested in braintract, braintract crossed within person)

egen specific_mask = group(braintract mask), label
mixed fa i.group#i.specific_mask i.sex age || id: , vce(robust)
margins specific_mask, dydx(group)

If I use

contrast

, can I get the same comparison?

Best regards,
Jack Liang