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data x;
input x y;
z=y>0+x>0;    --------改成z=y>0; 可以
cards;
1 2
0 1
-1 3
;
run;
得不到正确的结果，why？？


  data x;
input x y;
z=sum(sign(x) ,sign(y) ); 用符号函数可以解决
cards;
1 2
0 1
. 3
;
run;

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关键词：Data Input cards card sign

不明白你想干嘛...

1# lilinzhong

In view of the Order of Evaluation in Compound Expressions in SAS, the expression here z = y>0+x>0 is equivalent to z = (y>0+x)>0, but you were expecting z = (y>0)+(x>0). I think this is where the discrepancy comes from.    I would suggest that you properly using brackets to make the expression more explicit.

JingJu

lilinzhong 发表于 2010-2-3 16:18
data x;
input x y;
z=y>0+x>0;    --------改成z=y>0; 可以
cards;
1 2
0 1
-1 3
;
run;
得不到正确的结果，why？？


  data x;
input x y;
z=sum(sign(x) ,sign(y) ); 用符号函数可以解决
cards;
1 2
0 1
. 3
;
run;

Boolean value in SAS has one of only two values, {1, 0}    1=true , 0= false

In the case

z=y>0+x>0;

is the same as z=y>(0+x)>0; accoring to the operation order.
x  y
1 2        2>1>0   {true}    z=1;
0 1        1>0>0   {false}  z=0
-1 3       3>-1>0 {false}  z=0

That is what you see.

3# jingju11

the expression here z = y>0+x>0 is equivalent to z = (y>0+x)>0

Clearly I was wrong. Sorry about that and thanks for the correction. So,

z = y>0+x>0 is equivalent to z = (y>(0+x)>0)

JingJu

谢谢，解决了。果然如此，忽略了这个细节。