VPC question

Dear NM users, I have a basic VPC question. I run the following code to generate VPC plot using cluster: vpc run63.mod -lst=run63.lst -samples=1000 -idv=LAVES PlotVPC 7 I got the following error message. Reading /pkpd_ms/M4444/PPEN/npc_dir7/vpc_results.csv Error in xpose.VPC(vpc.file, vpctab = vpctab, PI = "both", PI.up.lty = 0, : trying to get slot "Data" from an object of a basic class ("NULL") with no slots Execution halted Could anybody kindly tell me what went wrong? Thank you very much, Rong Liu Associate Principle Scientist at Merck & Co., Inc Notice: This e-mail message, together with any attachments, contains information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station, New Jersey, USA 08889), and/or its affiliates Direct contact information for affiliates is available at http://www.merck.com/contact/contacts.html) that may be confidential, proprietary copyrighted and/or legally privileged. It is intended solely for the use of the individual or entity named on this message. If you are not the intended recipient, and have received this message in error, please notify us immediately by reply e-mail and then delete it from your system.