想要实现：从32个序列，即x1,x2...x32中任意选两个做格兰杰因果检验并记录结果。试过foreach，没能如愿。请老师指点。我的语句
global vars "x1 x2 x3 x5 x6 x7 x8 x9 x11 x12 x13 x14 x15 x16 x17 x18 x19 x20 x21 x22 x23 x24 x25 x26 x27 x28 x29 x30 x31 x32"
foreach v of varlist $vars{
  gcause `v' `v'+1, lags(40)
}
   
foreach num of numlist 1/32{
  gcause x`num', x`num++', lags(40)
  }