r - Select groups which have more than one variable in them -

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• remove ids occur x times r 2 answers

simple question. let's have dataframe looks this:

data.frame (species=c(a,a,b,c,c,d),dbh=c(5,4,7,1,3,6)) 

and want exclude species b , d because occur once, how can that?

this can done using either base r or using other packages. data.table, convert 'data.frame' data.table (setdt(df1)), grouped 'species', if number of rows greater 1 (.n>1) , subset of data.table (.sd)

 library(data.table)  setdt(df1)[, if(.n>1) .sd, species] 

or dplyr, use filter after grouping.

 library(dplyr)  df1 %>%      group_by(species) %>%      filter(n()>1) 

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the base r function ave can used well. group 'species', length, convert logical vector , subset dataset.

 df1[with(df1, ave(dbh, species, fun=length)>1),] 

or can use table frequency of elements in 'species'. find names of elements have more 1 count, use %in% logical vector , subset before.

 tbl <- table(df1$species)>1  df1[df1$species %in% names(tbl)[tbl],]