I should have added I am using R Studio, running R 2.14.1 64 bit on Win7 with all packages of Bioconductor up to date. Whether you think you can or think you can't - Your're right... Henry Ford Cristina Paul Citrus Quarantine Unit USDA-ARS-BA-PSI-MPPL Mailling address: Bldg 004 Rm 118 Beltsville MD 20705 office: 301-504-7657 FAX: 301-504-5449 Cell: 240-286-6709 Physical Address: Range 1 head house #6 This electronic message contains information generated by the USDA solely for the intended recipients. Any unauthorized interception of this message or the use or disclosure of the information it contains may violate the law and subject the violator to civil or criminal penalties. If you believe you have received this message in error, please notify the sender and delete the email immediately. [[alternative HTML version deleted]]