1. 问问题是不是选<疑难解惑>？？

2. 如果在proc tabulate里面使用class variable crossed with itself，就会出现WARNING: A class variable is crossed with itself in the table statement at line 1106.

比如下面这个例子，
proc tabulate data=sashelp.class;
class age sex;
var weight height;
table (sex all) (age all), (sex*rowpctn='' age*rowpctn='' weight*mean height*mean);
run;

log:
WARNING: A class variable is crossed with itself in the table statement at line 1264.  This may cause unpredictable results.
WARNING: A class variable is crossed with itself in the table statement at line 1264.  This may cause unpredictable results.
NOTE: There were 19 observations read from the data set SASHELP.CLASS.
NOTE: PROCEDURE TABULATE used (Total process time):
      real time           0.15 seconds
      cpu time            0.06 seconds

Output:

	Sex		Age						Weight	Height
	F	M	11	12	13	14	15	16	Mean	Mean
Sex	100	.	11.11	22.22	22.22	22.22	22.22	.	90.11	60.59
F
M	.	100	10	30	10	20	20	10	108.95	63.91
All	47.37	52.63	10.53	26.32	15.79	21.05	21.05	5.26	100.03	62.34
Age	50	50	100	.	.	.	.	.	67.75	54.4
11
12	40	60	.	100	.	.	.	.	94.4	59.44
13	66.67	33.33	.	.	100	.	.	.	88.67	61.43
14	50	50	.	.	.	100	.	.	101.88	64.9
15	50	50	.	.	.	.	100	.	117.38	65.63
16	.	100	.	.	.	.	.	100	150	72
All	47.37	52.63	10.53	26.32	15.79	21.05	21.05	5.26	100.03	62.34

求教大虾~