options ls=120;

filename foo2 url "http://www.uvm.edu/~abh/stat295/datasets/trees2002.dat";
filename foo4 url "http://www.uvm.edu/~abh/stat295/datasets/trees2004.dat";
filename foo6 url "http://www.uvm.edu/~abh/stat295/datasets/trees2006.dat";

data trees02;
     infile foo2;
	 input plot tree treatment $  dbh02;
run;

data trees04;
     infile foo4;
	 input plot tree treatment $  dbh04;
run;

data trees06;
     infile foo6;
	 input plot tree treatment $  dbh06;
run;

proc sort data=trees02;
     by plot tree;
run;

proc sort data=trees04;
     by plot tree;
run;

proc sort data=trees06;
     by plot tree;
run;

data trees020406;
     merge trees02 trees04 trees06;
	 by plot tree;
run;

proc print data=trees0206;
title "Tree diameters in 2002, 2004, and 2006";
run;