[R] Question in Using sink function

[Yao, Minghua]

Could anyone please explain to me why the following writes nothing into
"all.Rout"
file? If the "for" loop is removed, t.test output can be written into
"all.out".

Thanks in advance. 

Minghua Yao

 ......
  zz <- file("all.Rout", open="wt")
  sink(zz)
   
  for(i in 1:n)
  {	  
    Cy3<-X[,2*i-1];
    Cy5<-X[,2*i];
	
    t.test(Cy3, Cy5)
  }


  sink()
  close(zz)
......