Hi, On 11/12/18 17:08, Duncan Murdoch wrote: > The duplicated() function gives TRUE if an item in a vector (or row in > a matrix, etc.) is a duplicate of an earlier item. But what I would > like to know is which item does it duplicate? > > For example, > > v <- c("a", "b", "b", "a") > duplicated(v) > > returns > > [1] FALSE FALSE TRUE TRUE > > What I want is a fast way to calculate > > [1] NA NA 2 1 > > or (equally useful to me) > > [1] 1 2 2 1 > > The result should have the property that if result[i] == j, then v[i] > == v[j], at least for i != j. > > Does this already exist somewhere, or is it easy to write?
I generally use match() for that: > v <- c("a", "b", "b", "a") > match(v, v) [1] 1 2 2 1 H. > > Duncan Murdoch > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://urldefense.proofpoint.com/v2/url?u=https-3A__stat.ethz.ch_mailman_listinfo_r-2Dhelp&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=APEsp-OzJs6YdfshtiYe715BsAor8xTu26lpN4KGOrU&s=opxT_5og2YaWKdiXD-cRz0gWxGGMRG6kq20Jo8711qA&e= > > > PLEASE do read the posting guide > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.R-2Dproject.org_posting-2Dguide.html&d=DwICAg&c=eRAMFD45gAfqt84VtBcfhQ&r=BK7q3XeAvimeWdGbWY_wJYbW0WYiZvSXAJJKaaPhzWA&m=APEsp-OzJs6YdfshtiYe715BsAor8xTu26lpN4KGOrU&s=ZaPnASTzuEmE8EHqFL6F5wYkPhhg_uv-CMrGjY2-_Q4&e= > and provide commented, minimal, self-contained, reproducible code. -- Hervé Pagès Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpa...@fredhutch.org Phone: (206) 667-5791 Fax: (206) 667-1319 ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.