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2009 Oct 26
3
Sandard deviation calculation
Dear all I am trying to learn R I was trying to calculate standard deviation here are the commands and outputs in R > sd(Ht_cm[type=='SD'])[1] 3.283605> sd(Ht_cm[from_treeline=='above'])[1] 16.83289> sd(Ht_cm[type=='SD'][from_treeline=='above'])[1] NA> the problem is that, i could not understand why the third command could not give any result.