search for: birdnerd

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2010 Jun 13
5
Count of unique factors within another factor
I have a data frame with two factors (sampling 'unit', 'species'). I want to calculate the number of unique 'species' per 'unit.' I can calculate the number of unique values for each variable separately, but can't get a count for each ?unit?. > data=read.csv("C:/Desktop/sr_sort_practice.csv") > attach(data) > data[1:10,] unit species 1