Is there any way to define a frequency range for the EIG and/or EIGs function to solve for the eigenvalues and eigenvectors?

Hello everyone,

Is there any way to define a frequency range for the EIG and/or EIGs function to solve for the eigenvalues and eigenvectors? For instance, could we set the range to be -1 Hz to 50 Hz? We have to generate the eigenvalues and eigenvectors of the delivered math models (mass and stiffness matrices) given to us. We get very large math models on the order of 14,000 degrees of freedom. Thus, when we run Matlab to generate the eigenvalues and eigenvectors, it takes multiples hours for EACH model since the EIG and EIGS function calculates ALL of the eigenvalues and eigenvectors. Then, our next step is to reduce the eigenvalues and eigenvectors to the frequency range we need. I know the EIG and EIGS function will not calculate ALL eigenvalues and eigenvectors if you know how many of those you want. However, we don’t know how many we need – again, it is the frequency range we want to have calculated. Note that programs like Nastran can generate the eigenvalues and eigenvectors for a given frequency range. Is there a way to do this in Matlab? Is there another function that would quickly tell you how many modes are needed? I appreciate the help with this.