以下是原始代码，来自http://www.ats.ucla.edu/stat/stata/faq/modmed.htm.

quietly summarize w
global m=r(mean)
global s=r(sd)
generate wx=w*x  

capture program drop bootm2
program bootm2, rclass
  sureg (m x w wx)(y m x w wx)
  return scalar cielw = ([m]_b[x]+($m-$s)*[m]_b[wx])*[y]_b[m]
  return scalar ciemn = ([m]_b[x]+($m)*[m]_b[wx])*[y]_b[m]
  return scalar ciehi = ([m]_b[x]+($m+$s)*[m]_b[wx])*[y]_b[m]                       
end

bootstrap r(cielw) r(ciemn) r(ciehi), reps(500) nodots: bootm2




我修改了这段代码，修改的代码如下

quietly summarize w
global m=r(mean)
global s=r(sd)
generate wx=w*x  

capture program drop bootm1
program bootm1, rclass
  reg m x w wx
  nbreg y m x w wx
  return scalar cielw = ([m]_b[x]+($m-$s)*[m]_b[wx])*[y]_b[m]
  return scalar ciemn = ([m]_b[x]+($m)*[m]_b[wx])*[y]_b[m]
  return scalar ciehi = ([m]_b[x]+($m+$s)*[m]_b[wx])*[y]_b[m]                       
end

bootstrap r(cielw) r(ciemn) r(ciehi), reps(500) nodots: bootm1

但是stata reported equation [m] not found
an error occurred when bootstrap executed bootm1
有谁知道如何解决这个问题吗？非常感谢