原先一直用eviews，这次数据时=是stata，在打开一个38m的数据，提示no room to add more variables，An attempt was made to add a variable that would have resulted in
    more than 5000 or 4999 variables (Stata reserves one variable for
    its own use).  You have the following alternatives:
     1.  Drop some variables; see help drop.
     2.  If you are using Stata/SE, increase maxvar; see help maxvar.
r(900);
按照提示drop all.
set mem 512,perm
set mat 800,perm
可还是不行，望赐教，在线等。