我的思路是：
data b;
  set a;
  arm=1;output b(keep=id name age rename=(age=value));
  arm=2;output b(keep=id name height rename=(height=value));
  arm=3;output b(keep=id name weight rename=(weight=value));
  arm=4;output b(keep=id name country rename=(country=value));
run;
但是运行不出来！

data b;
set a;
array var{*} age height weight;
length value $8.;
do arm = 1 to 4;
        if arm <=3 then value = var[arm];
        else value = country;
        output;
end;
keep d name value arm;
run;

transpose 是可以做互逆过程的，
by id name;
var  age height weight country;
然后按_name_变量排序应该就可以得到了，需要加arm变量的话对_name_变量按age、height、weight、countrty加个order,在排序就好了

帅，让我对transpose又有了更深一层的认识！