如下所示，有一个列表boot，boot[[i]]为列表中的i个向量， i=1:5 。我想统计不同向量中元素出现的次数和元素所对应的值，例如元素X597s共出现5次，分别为2.888135e-06，6.960930e-10，1.578643e-08，1.400029e-06和2.817243e-05。

各位高手，该如何做呢?

> boot[[1]]
              [,1]
X711s 2.609689e-07
X709s 1.773618e-09
X597s 2.888135e-06
X691s 2.605330e-06
X653s 1.797357e-09
X654s 1.908793e-03
X456s 3.899673e-07
X460s 1.465550e-07
X613s 2.761623e-06
X573s 1.829730e-06
X443s 1.089032e-06
X475s 3.624400e-05
X469s 1.197439e-04
X439s 1.557444e-07
X642s 6.916490e-04
X566s 1.298924e-04
X717s 2.484436e-04
> boot[[2]]
              [,1]
X597s 6.960930e-10
X711s 7.113927e-12
X709s 1.687318e-12
X681s 1.106795e-10
X686s 2.502877e-08
X660s 9.447526e-11
X576s 3.623954e-10
X435s 4.567568e-08
X456s 1.963852e-03
X613s 3.479552e-10
X487s 2.805565e-05
X503s 2.644120e-05
X619s 2.079563e-07
X488s 1.244784e-03
X602s 2.374765e-05
X614s 5.436600e-07
X716s 6.355726e-06
X650s 2.701211e-03
X443s 1.518455e-05
X476s 7.303409e-06
X536s 7.204384e-04
> boot[[3]]
              [,1]
X691s 1.876003e-10
X597s 1.578643e-08
X721s 2.371441e-07
X716s 4.852170e-06
X686s 3.627151e-11
X490s 2.320861e-05
X508s 1.099071e-05
X713s 2.768126e-06
X663s 9.028564e-10
X516s 1.300785e-05
X610s 3.442536e-05
X493s 7.771606e-04
X501s 1.076061e-05
X689s 4.045847e-05
X486s 1.122411e-05
X613s 1.375760e-03
X566s 1.383331e-03
> boot[[4]]
              [,1]
X597s 1.400029e-06
X691s 7.136585e-06
X569s 3.290512e-07
X471s 1.234949e-04
X488s 6.671308e-04
X673s 8.456763e-05
X665s 5.890863e-07
X668s 1.938105e-03
X550s 1.944471e-05
> boot[[5]]
              [,1]
X597s 2.817243e-05
X711s 1.538649e-05
X709s 7.290627e-04
X691s 3.825125e-05
X677s 6.775898e-05
X680s 4.879904e-04
X713s 1.137613e-04
X716s 5.303257e-04