local cell=No in -1

gen str2aa4=""

for var a1-a10:replaceX=0 if X==.

genWeighteda4=a4*weight                 

by code:egenvmedian=median(Weighteda4) if answer==0

by code:egenvquartile=pctile(Weighteda4) if answer==0,p(75)

麻烦各位能帮我解释一下这几句的意思吗？，谢谢