[R] finding those elements of listA that are found in listB

John Sorkin JSorkin at grecc.umaryland.edu
Thu Sep 17 04:43:04 CEST 2015

I have two structures. I think they are lists, but I am not sure. Both structures contain integers. I am trying to find those members of list b that are found in list a. I have tried to perform the search using grep, but I get an error. Please see code below. I would appreciate knowing how to search listB for any element in listA

> str(listA)
 int [1:42] 13083 13705 14123 14168 14382 14652 14654 14678 14817 14822 ...
> str(listB)
 int [1:633] 13083 13083 13083 13083 13083 13083 13705 13705 13705 13705 ...
> grep(listA,listB)
[1] 1 2 3 4 5 6
Warning message:
In grep(listA, listB) :
  argument 'pattern' has length > 1 and only the first element will be used


John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
Baltimore VA Medical Center
10 North Greene Street
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing) 

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