例1
>x2 <- pi * 100^(-1:3)
>signif(x2, 3)
[1] 3.14e-02 3.14e+00 3.14e+02 3.14e+04 3.14e+06
however,
例2
>x=0.2
>signif(x, 3)
[1] 0.2
为啥不行呢？有点郁闷