duplicates() function
On 08/04/2011 11:08 AM, Joshua Ulrich wrote:
How about: y<- rep(NA,length(x)) y[duplicated(x)]<- match(x[duplicated(x)] ,x)
That's a nice solution for vectors. Unfortunately for me, I have a matrix (which duplicated() handles by checking whole rows). So a better example that I should have posted would be x <- cbind(1, c(9,7,9,3,7) ) and I'd still like the same output
duplicated(x)
[1] FALSE FALSE TRUE FALSE TRUE
duplicates(x)
[1] NA NA 1 NA 2 Duncan Murdoch
-- Joshua Ulrich | FOSS Trading: www.fosstrading.com On Fri, Apr 8, 2011 at 9:59 AM, Duncan Murdoch<murdoch.duncan at gmail.com> wrote:
I need a function which is similar to duplicated(), but instead of returning TRUE/FALSE, returns indices of which element was duplicated. That is,
x<- c(9,7,9,3,7) duplicated(x)
[1] FALSE FALSE TRUE FALSE TRUE
duplicates(x)
[1] NA NA 1 NA 2 (so that I know that element 3 is a duplicate of element 1, and element 5 is a duplicate of element 2, whereas the others were not duplicated according to our definition.) Is there a simple way to write this function? I have an ugly implementation in R that loops over all the values; it would make more sense to redo it in C, if there isn't a simple implementation I missed. Duncan Murdoch
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