Note: For the node matching algorithm, the MAC Calculator will probably not give correct results for cases where you have several nodes in the same location, as with remote points. This limitation is related to the fact that this algorithm matches nodes according to location, so it is not possible to distinguish between them and it will randomly pick one of them.
The modal assurance criterion (MAC) can compare two real solutions or two complex solutions.
The MAC between two real solutions is computed using the equation:
where:
= the ith solution vector of
solution 1.
= the jth solution vector of
solution 2.
= diagonal of the mass matrix used in obtaining solution k. The MAC between two complex
solutions is computed using the equation:
where:
= the complex conjugate of a complex vector 
.
In the case of MAC between a real and a complex solution, you can select one of two methods for the calculation:
Complex to Real Projection property set to - takes the real part of the complex solution and uses the Real to Real formulation.
Complex to Real Projection property set to - takes the Complex to Real Projection Methodology to convert the complex solution into a real solution, using the Real to Real formulation.
The modal assurance criterion is not weighted by mass. That is, the mass is assumed to be equal at all degrees of freedom in cases where:
The diagonal of the mass matrix is not available, for example with non-structural degrees of freedom.
The model is solved with cyclic symmetry.
The dot product of the solution vectors is calculated:
At matched nodes if the Data Interpolation property is set to , and at mapped nodes if it is set to .
At DOFs selected in the Degrees of Freedom property.