即可能得到的结果为：
a b c
1 4 3
1 4 5
1 6 7
2 11 9
2 10 11
2 12 13
谢谢啦！作者: Qiong 时间: 2011-1-19 11:53 标题: Re: 有后面的观测赋值个第一个观测 土法，凑合用
[code:3dh5sz34]data vk ;
input a b c;
cards;
1 2 3
1 4 5
1 6 7
2 8 9
2 10 11
2 12 13
;
run;
data vk2;
retain new 0;
set vk;by a notsorted;
new= new*(1-first.a)+1;
rename b=newb c=newc;
if new=2;
run;
data vk ;
merge vk vk2;
by a;
if first.a then do;x=RAND('BERNOULLI',0.5);b= x*newc+(1-x)*newb; end;
drop new:;
run;
proc print;
run;[/code:3dh5sz34]作者: shiyiming 时间: 2011-1-21 00:06 标题: Re: 有后面的观测赋值个第一个观测 to vicky1020: learn a lot from you, thank you!
And I have not found other code besides the following trivial code.
[code:swajljf9]
data out(keep=a b c);
set raw end=last;
by a;
if first.a then do;
array raw{2} b c;
array temp{2};
do i=1 to 2;
temp[i]=raw[i];
end;
index=_n_+1;
set raw point=index;
if 0<ranuni(123)<=0.5 then raw[2]=temp[2];
else do;
raw[1]=raw[2];
raw[2]=temp[2];
end;
end;
output;
if last then stop;
run;
[/code:swajljf9]作者: shiyiming 时间: 2011-1-21 01:24 标题: Re: 有后面的观测赋值个第一个观测 to hairul
啊。写得很好啊。