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Hi, I am trying to identify duplicate values in a column in a date frame. The duplicated function identifies the duplicate rows in the data frame but it only does this for the second record, not both records. Is there a way to mark both rows in the data frame as TRUE? dfA$dups<-duplicated(dfA$Value) dfA Site State Value dups 929 VA 73 FALSE 929 VA 73 TRUE 930 VA 76 FALSE 930 VA 76 TRUE 931

Hi, I am R beginner and am trying to figure out how to generate a complete list of species for every point, visit, and year. The code below is close but does not give me a list of species for every point, visit, and year in my data set. spplist<-unique(sumPtCt$Species) spplength<-length(spplist) Pointlist<-unique(sumPtCt$Point) Pointlength<-length(Pointlist)

Hi, I have a dataset in which I would like to select rows based on matching conditions and return the maximum value of a variable else return one row if duplicate counts exist. My dataset looks like this: PGID PTID Year Visit Count 6755 53121 2009 1 0 6755 53121 2009 2 0 6755 53121 2009 3 0 6755 53122 2008 1 0 6755 53122 2008 2 0 6755 53122 2008 3 1 6755 53122 2009 1 0 6755 53122 2009 2 1 6755

Hi, I am relatively new to R and I am trying to figure out how to select rows of my data based on a condition. For example in the dataset below multiple observers recorded data at the same point on the same date and the data was recorded on separate rows, but I only need one of the rows of data. Is it possible to use grep to search for rows that have matching PtName and Date and then select the