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Quick Data Summaries in SAS • Start by bringing in data – Use permanent data set for these examples • Proc Summary – Produces summaries relatively easily – Designed to produce a table of output that can be manipulated further ***This is a critical difference from tabulate*** – Need to pre-sort data by any “by” groups – Need to print out results Quick Data Summaries in SAS • Basic Summary Syntax: Proc sort; By var1 var2; Run; Proc summary; By var1 var2; Var variable3; Output out=new_table mean=mean_name n=n_name….; Run; Proc print; Run; Statistics available in Proc Summary • Mean, n, standard deviation, standard deviation, variance, coefficient of variation, sum • Minimum, maximum, range, number of missing observations, median Some Quirks of Proc Summary • Whenever you use proc summary, it adds two new variables: _type_ and _freq_ (note underscores at beginning and end of variable names – _freq_ indicates the number of observations – _type_ indicates whether the output is a matrix or not • You can ignore these variables in virtually all cases • You need to remember what is the “active” dataset, or specify the dataset that summary will operate on – The active dataset is the most recently used dataset by default Shannon’s Diversity Index H= -∑ pi ln(pi)