需要将样本筛选成平衡面板数据。
id表示公司代码，t=1,2，....50，表示第几周，r表示股票的周回报率。
数据总数是73446。

输入 xtbalance, range（1 50）命令后，出现如下红字：
no room to add more variables because of width
    An attempt was made to add a variable that would have increased the memory required to store an observation beyond what is
    currently possible.  You have the following alternatives:
     1.  Store existing variables more efficiently; see help compress.
     2.  Drop some variables or observations; see help drop.  (Think of Stata's data area as the area of a rectangle; Stata can
         trade off width and length.)
     3.  Increase the amount of memory allocated to the data area using the set memory command; see help memory.
r(903);

我分别输入了  set memory 1g； set memory 100m等命令，依然不行：
set memory 1g
no; data in memory would be lost
r(4);
. set memory 100m
no; data in memory would be lost
r(4);

请问我该如何处理？？？