data a; set sasuser.trees; 
proc print;
proc transpose data=a out=b prefix=week; by tree; var Y;  
proc print; 
proc transpose data=b out=trees prefix=tree; var week1-week7;
proc print; 
data trees; set trees; drop _name_; 
retain date "01may2005"d; 
date = intnx("week",date,2); 
format date date7.; 
proc print; 
run; 
proc gplot; plot (tree1-tree5)*date/overlay; 
symbol1 v=none i=join; 
run;