Hello all,      I am looking for an IDL function to calculate the eigenvalues and eigenvectors of a Hermitian complex matrix, where the matrix is specified in sparse matrix form,  i.e. something like B=sprsin(A) eigenvalues=WantedFunction(B). I would like to specify a numerical range for which the eigenvalues should be returned.  This is possible with LA_EIGENQL but one has to enter the full matrix, with all the zeros.  I have looked at the IDL Analyst routines and have found IMSL_SP_LUSOL and IMSL_SP_LUFAC and others, but none that appears to have the functionality described above.   Best wishes, Philip.