<div>Andrew,</div> <div> </div> <div>Thanks in advance.</div> <div> </div> <div>I have run your code and it works well. Will you please clarify the error below:</div> <div> </div> <div>Error in getrffBeta("BNI", span = 60) : could not find function "rollapply".<BR></div> <div>It is required to put appropriate package using require(?) to incorporate the function "rollapply".</div> <div> </div> <div>May I request you to provide some literature on above topics.</div> <div> </div> <div>Thanks,</div> <div> </div> <div>Deb</div> <div><BR>Note: forwarded message attached.</div><p>