如何提取R中列表元素的名称？
列表元素的名称可以通过使用names函数来提取。例如，如果我们有一个定义为List的列表，其中包含三个名称分别为element1，element2和element3的元素，则可以使用以下命令从List中提取这些名称：
names(List)
例1
> List1<-list(x1=rnorm(50),x2=rnorm(50,1,0.28),x3=rnorm(50,5,2.1)) > List1
输出结果
$x1 [1] -0.04518909 -0.22779868 0.24339595 -0.86189295 -0.73387277 -0.75313131 [7] 0.39694608 2.30565359 0.55670193 0.21973762 0.62968128 -0.90936921 [13] 1.33946741 -0.16315751 0.31357793 0.40365980 -0.23639612 -2.48749453 [19] 0.52152768 -1.57059863 0.51728464 0.98177111 0.65475629 0.23715538 [25] -0.71796609 -0.42731839 0.32335282 -0.90013122 -0.84549927 -0.88358214 [31] -0.32066379 -0.98945433 0.42469849 -1.63095343 0.32584448 0.10947333 [37] 0.23486625 0.28166351 1.18432843 0.94828212 0.09452671 0.56618262 [43] 0.52839533 1.22136242 0.76011311 0.11757345 2.47459913 -0.47890572 [49] -1.91918520 -0.02408708 $x2 [1] 0.8270975 0.9756136 1.1292744 1.0656721 0.7703431 0.8769942 1.1293051 [8] 1.0581120 1.0815165 1.2847627 0.6654920 1.2342987 0.6837453 1.2018498 [15] 1.0908703 1.1193189 0.5471691 1.0213345 0.8050452 0.4815627 0.6849457 [22] 0.8577580 1.1381807 1.0131761 1.2062184 0.7610613 1.3568787 0.9533896 [29] 1.2557551 0.4617964 0.8776077 1.3058164 1.1131230 1.2142810 0.9978407 [36] 0.7247716 1.4211604 0.5994001 0.7525555 1.4627048 0.7734563 0.8280289 [43] 0.9735345 1.0476358 1.1781612 0.8641444 1.0304007 0.6046310 0.8035452 [50] 0.7185106 $x3 [1] 2.617699 6.486300 3.796717 2.448953 8.561896 6.948493 6.174320 5.890213 [9] 6.333487 1.866408 4.988860 5.306587 6.862673 2.881893 2.172200 3.583765 [17] 3.830627 3.403771 6.404305 4.417270 4.538683 2.788276 4.869081 7.097852 [25] 2.967966 4.711434 5.088199 8.753127 5.219092 6.472948 3.698116 3.735600 [33] 5.301249 3.958626 2.951177 1.139676 5.973805 3.137057 5.817388 6.123433 [41] 5.380026 8.153839 4.524674 2.266312 2.914673 3.633610 5.324451 5.095410 [49] 5.221360 1.832700
示例
> names(List1)
输出结果
[1] "x1" "x2" "x3"
例2
> List2<-list(x1=rpois(50,5),x2=rpois(50,1),x3=rpois(50,5),x4=rpois(50,8),x5=rpois(50,10)) > List2
输出结果
$x1 [1] 7 7 6 4 2 5 5 7 7 4 9 3 2 3 1 7 3 5 4 6 7 4 7 8 2 [26] 2 9 5 8 3 7 6 4 11 4 7 4 6 6 4 3 7 5 4 7 4 7 5 4 3 $x2 [1] 1 0 1 2 0 2 2 0 2 3 1 3 2 1 1 1 1 2 1 2 1 1 0 0 0 0 3 0 1 0 1 1 3 0 1 0 2 1 [39] 1 1 0 0 0 0 2 2 1 0 2 1 $x3 [1] 3 7 7 8 2 4 6 7 8 3 6 8 2 6 4 5 6 6 4 4 9 4 5 4 5 [26] 4 5 5 8 0 5 6 3 3 6 12 2 7 4 4 7 6 7 2 6 7 11 13 5 6 $x4 [1] 7 7 8 15 5 6 12 12 6 6 4 9 11 12 6 11 15 13 10 8 9 6 10 12 10 [26] 8 8 8 8 9 6 9 7 9 8 5 5 9 10 8 5 6 8 12 8 11 9 8 9 6 $x5 [1] 9 10 9 9 6 7 8 6 13 12 14 7 8 13 8 8 10 8 10 10 9 7 9 7 4 [26] 11 5 7 18 10 12 6 11 13 13 5 12 15 9 6 5 12 9 10 10 4 11 6 12 15
示例
> names(List2)
输出结果
[1] "x1" "x2" "x3" "x4" "x5"
例子3
> List3<-list(x1=runif(50,2,5),x2=runif(50,1,5),x3=runif(50,5,10)) > List3
输出结果
$x1 [1] 4.413341 3.318683 2.450609 3.117884 3.347430 2.167973 4.473528 3.308317 [9] 2.891431 3.259983 2.101081 2.489383 2.727202 4.103531 2.061813 2.126091 [17] 4.590316 4.890000 2.725137 4.086082 3.798446 2.682532 3.600169 4.228952 [25] 2.264763 4.732312 3.053867 2.090457 3.528672 3.097195 2.808085 4.666389 [33] 3.644389 4.517354 4.119483 4.859402 3.091996 2.886587 4.989477 2.945724 [41] 4.262805 2.757937 2.320727 3.989926 2.747881 3.432197 4.045197 2.313279 [49] 2.873494 4.004079 $x2 [1] 3.863761 3.060900 3.088654 1.429419 1.501166 3.371164 3.016494 2.433578 [9] 3.644674 2.931639 4.553203 1.309591 1.696542 4.647760 4.973822 3.630334 [17] 1.494571 2.141640 3.337546 3.793574 3.544146 3.906353 3.318471 1.653554 [25] 4.452764 2.863841 3.988762 4.696605 2.372169 3.913032 4.068302 4.211055 [33] 2.796389 4.569563 1.362797 1.360992 1.562173 3.539244 1.588572 2.740451 [41] 1.512468 2.503382 1.298349 1.508630 2.195898 4.040723 2.272298 4.225725 [49] 4.682531 3.030588 $x3 [1] 7.904580 9.373170 5.687662 5.615320 6.170858 9.833555 6.421968 8.256569 [9] 5.255653 9.225753 6.719730 9.973355 7.186546 6.466654 7.712851 7.791231 [17] 9.460951 8.485921 6.945822 6.276568 5.247020 8.141602 6.575557 7.804101 [25] 7.483326 7.482139 8.670358 5.600923 6.953811 8.090939 9.176059 7.189967 [33] 5.356993 8.398447 5.429305 7.351870 6.970362 6.780346 7.637896 8.434442 [41] 9.261975 5.176213 8.207120 5.733510 7.102484 7.958931 5.799031 7.223153 [49] 5.255746 5.394654
示例
> names(List3)
输出结果
[1] "x1" "x2" "x3"
例子4
> List4<-list(y1=rexp(50,1.12),y2=rexp(50,2.1)) > List4
输出结果
$y1 [1] 0.806148350 1.458187265 0.534007093 0.950131273 0.217697643 0.349654709 [7] 0.874155289 2.004103178 0.362298127 0.533686567 0.611537599 0.136836959 [13] 0.198465017 0.516533088 0.705214297 0.348598974 0.385648527 0.257238782 [19] 0.131113534 0.456706525 4.077398554 0.501530183 1.094008447 0.279010694 [25] 2.271581539 0.342538455 0.077849912 0.502802631 1.844349116 0.297917889 [31] 0.081726119 1.545759146 1.119755295 0.006217782 1.711755760 0.227284939 [37] 1.391966260 0.845130298 1.719655529 0.519416726 0.898552797 0.208143165 [43] 2.520577533 1.670047493 0.756593752 0.361542577 2.468861275 0.280330950 [49] 0.336729084 6.532385077 $y2 [1] 0.139012937 0.751480073 0.071020098 0.786773500 0.372965729 0.037590902 [7] 0.167700221 0.092755225 0.787360131 0.107568293 2.268001886 0.444335844 [13] 0.074739241 0.151111998 0.184172284 0.581389785 0.014686120 0.820748947 [19] 0.107117694 0.327100046 0.200850286 0.076522915 0.201419763 0.122467053 [25] 0.192721591 0.189551687 0.278166513 0.299343658 0.149084151 0.958924542 [31] 0.034754787 0.004645119 0.670121429 1.347222694 0.642560074 0.023936619 [37] 0.575837008 0.768578674 0.196833013 2.178089408 0.331298845 1.839747737 [43] 0.594427700 0.700286120 0.224447412 0.523475388 0.364124369 0.617526646 [49] 0.482226880 1.318312322
示例
> names(List4)
输出结果
[1] "y1" "y2"