rc2ac a = rc2ac(k, R0) k: Lattice form reflection coefficients. r0: Initial zero lag autocorrelation. a: Autocorrelation coefficients. Uses rlevinson to function convert reflection coefficients to autocorrelation sequence. r = rc2ac(k,r0) finds the autocorrelation coefficients, r, of the output of the discrete-time prediction error filter from the lattice-form reflection coefficients k and initial zero-lag autocorrelation r0