如何提取R中不包含NULL的列表元素？
列表有时包含NULL元素以及其他元素。因此，我们可能希望摆脱该NULL元素，以便我们可以轻松使用列表。为此，我们可以使用具有以下语法的lapply函数-
语法
“List_name”[!unlist(lapply(“List_name”,is.null))]
示例
请看以下列表-
x1<-LETTERS[1:20] x2<-sample(1:50,30) x3<-rpois(50,5) x4<-NULL x5<-sample(1:10,20,replace=TRUE) x6<-sample(1:10,50,replace=TRUE) x7<-NULL List<-list(x1,x2,x3,x4,x5,x6,x7) List
输出结果
[[1]] [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" [20] "T" [[2]] [1] 27 38 3 48 16 17 50 8 31 21 34 37 46 18 7 11 29 9 49 45 12 44 32 4 13 [26] 22 43 35 39 20 [[3]] [1] 4 4 6 5 4 11 3 2 4 7 2 0 2 3 9 2 4 8 7 6 4 3 2 8 6 [26] 9 7 5 5 5 3 8 5 1 6 6 2 4 2 4 2 5 4 5 3 2 10 7 5 7 [[4]] NULL [[5]] [1] 4 5 3 9 5 1 8 7 5 1 10 9 10 4 4 8 7 3 6 1 [[6]] [1] 6 4 8 5 5 10 7 5 3 7 10 5 8 1 10 9 3 8 2 5 9 3 5 9 6 [26] 5 8 6 3 10 6 3 8 4 10 5 3 7 3 4 5 6 1 8 6 6 9 2 5 4 [[7]] NULL
提取不为NULL的列表元素-
示例
List[!unlist(lapply(List,is.null))]
输出结果
[[1]] [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" [20] "T" [[2]] [1] 27 38 3 48 16 17 50 8 31 21 34 37 46 18 7 11 29 9 49 45 12 44 32 4 13 [26] 22 43 35 39 20 [[3]] [1] 4 4 6 5 4 11 3 2 4 7 2 0 2 3 9 2 4 8 7 6 4 3 2 8 6 [26] 9 7 5 5 5 3 8 5 1 6 6 2 4 2 4 2 5 4 5 3 2 10 7 5 7 [[4]] [1] 4 5 3 9 5 1 8 7 5 1 10 9 10 4 4 8 7 3 6 1 [[5]] [1] 6 4 8 5 5 10 7 5 3 7 10 5 8 1 10 9 3 8 2 5 9 3 5 9 6 [26] 5 8 6 3 10 6 3 8 4 10 5 3 7 3 4 5 6 1 8 6 6 9 2 5 4
让我们看另一个例子-
示例
y1<-runif(45,5,10) y2<-rexp(30,5) y3<-rpois(50,5) y4<-rbinom(50,10,0.5) y5<-rnorm(50,2,5) y6<-sample(1:10,50,replace=TRUE) y7<-NULL y8<-sample(1:20,50,replace=TRUE) y9<-LETTERS[1:26] y10<-1:50 New_List<-list(y1,y2,y3,y4,y5,y6,y7,y8,y9,y10) New_List
输出结果
[[1]] [1] 6.873191 6.832051 7.994383 5.560593 5.948195 6.148714 9.089198 8.024749 [9] 5.358905 8.940129 9.813643 5.225109 8.198397 6.791847 9.445375 9.296775 [17] 8.978427 9.823661 9.559257 9.600359 7.107150 9.533786 9.437307 5.852952 [25] 9.104474 8.204243 5.467284 5.643628 5.698499 5.586102 7.165100 9.540500 [33] 6.690515 9.422854 9.663365 6.047424 9.512649 5.237828 5.176613 9.307774 [41] 9.214194 5.736416 6.611679 9.158329 8.125111 [[2]] [1] 9.327297e-02 2.628267e-02 5.837356e-01 5.526928e-01 1.493052e-01 [6] 4.684264e-05 1.109019e-02 1.632936e-01 8.791466e-02 1.389368e-01 [11] 6.252034e-02 1.838558e-01 6.541021e-02 6.040159e-01 4.687270e-02 [16] 4.825074e-01 2.566619e-01 1.121949e-01 6.038569e-01 1.542802e-01 [21] 4.781870e-01 4.814911e-02 1.001143e-02 3.015966e-01 7.467835e-02 [26] 1.958277e-01 1.115525e-01 1.445676e-01 2.605108e-01 1.109321e+00 [[3]] [1] 5 7 3 2 5 5 2 9 10 4 3 2 4 5 3 5 7 1 8 6 3 11 6 3 9 [26] 9 1 4 6 5 5 3 7 4 6 4 1 7 5 8 5 3 4 9 4 5 3 5 8 6 [[4]] [1] 5 4 2 4 4 7 8 6 5 3 5 5 4 3 5 4 5 8 4 6 7 4 9 7 2 1 6 6 5 3 5 4 5 5 3 4 2 5 [39] 6 6 3 5 5 3 6 5 5 6 4 5 [[5]] [1] -4.9037570 0.2327350 6.0266983 2.5974054 7.0022107 -6.1438301 [7] 8.7918581 8.4450933 -0.5585743 2.0662291 10.1116677 2.3497613 [13] -0.4061269 -1.1139795 7.3350721 2.5669137 7.3098503 -0.4888469 [19] 4.8192636 10.4241038 -1.3895469 -4.9470356 -0.5330585 6.0830108 [25] 0.3959233 4.4163268 -5.4136557 5.2560139 5.4981337 -4.6610475 [31] -4.1390856 -7.5773305 1.9526344 2.4610800 10.0877877 3.8905763 [37] 2.9887570 4.8073600 6.1438959 2.9197778 -6.8822575 4.5946571 [43] 1.1602598 -4.0467120 5.2462252 10.2414053 -0.7420613 -2.3959838 [49] -3.2863947 6.5189106 [[6]] [1] 9 7 5 7 6 2 1 7 6 7 10 5 9 10 4 4 8 6 10 3 10 1 5 10 1 [26] 4 7 10 6 6 7 1 3 5 6 5 1 9 4 5 5 1 1 9 7 6 4 4 5 10 [[7]] NULL [[8]] [1] 13 2 9 3 18 2 16 4 8 3 7 3 3 2 3 9 15 4 8 14 17 4 15 20 20 [26] 3 4 6 11 6 14 4 15 18 5 9 19 7 3 18 6 2 4 18 3 4 19 15 17 8 [[9]] [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" [20] "T" "U" "V" "W" "X" "Y" "Z" [[10]] [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 [26] 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
示例
New_List[!unlist(lapply(New_List,is.null))]
输出结果
[[1]] [1] 6.873191 6.832051 7.994383 5.560593 5.948195 6.148714 9.089198 8.024749 [9] 5.358905 8.940129 9.813643 5.225109 8.198397 6.791847 9.445375 9.296775 [17] 8.978427 9.823661 9.559257 9.600359 7.107150 9.533786 9.437307 5.852952 [25] 9.104474 8.204243 5.467284 5.643628 5.698499 5.586102 7.165100 9.540500 [33] 6.690515 9.422854 9.663365 6.047424 9.512649 5.237828 5.176613 9.307774 [41] 9.214194 5.736416 6.611679 9.158329 8.125111 [[2]] [1] 9.327297e-02 2.628267e-02 5.837356e-01 5.526928e-01 1.493052e-01 [6] 4.684264e-05 1.109019e-02 1.632936e-01 8.791466e-02 1.389368e-01 [11] 6.252034e-02 1.838558e-01 6.541021e-02 6.040159e-01 4.687270e-02 [16] 4.825074e-01 2.566619e-01 1.121949e-01 6.038569e-01 1.542802e-01 [21] 4.781870e-01 4.814911e-02 1.001143e-02 3.015966e-01 7.467835e-02 [26] 1.958277e-01 1.115525e-01 1.445676e-01 2.605108e-01 1.109321e+00 [[3]] [1] 5 7 3 2 5 5 2 9 10 4 3 2 4 5 3 5 7 1 8 6 3 11 6 3 9 [26] 9 1 4 6 5 5 3 7 4 6 4 1 7 5 8 5 3 4 9 4 5 3 5 8 6 [[4]] [1] 5 4 2 4 4 7 8 6 5 3 5 5 4 3 5 4 5 8 4 6 7 4 9 7 2 1 6 6 5 3 5 4 5 5 3 4 2 5 [39] 6 6 3 5 5 3 6 5 5 6 4 5 [[5]] [1] -4.9037570 0.2327350 6.0266983 2.5974054 7.0022107 -6.1438301 [7] 8.7918581 8.4450933 -0.5585743 2.0662291 10.1116677 2.3497613 [13] -0.4061269 -1.1139795 7.3350721 2.5669137 7.3098503 -0.4888469 [19] 4.8192636 10.4241038 -1.3895469 -4.9470356 -0.5330585 6.0830108 [25] 0.3959233 4.4163268 -5.4136557 5.2560139 5.4981337 -4.6610475 [31] -4.1390856 -7.5773305 1.9526344 2.4610800 10.0877877 3.8905763 [37] 2.9887570 4.8073600 6.1438959 2.9197778 -6.8822575 4.5946571 [43] 1.1602598 -4.0467120 5.2462252 10.2414053 -0.7420613 -2.3959838 [49] -3.2863947 6.5189106 [[6]] [1] 9 7 5 7 6 2 1 7 6 7 10 5 9 10 4 4 8 6 10 3 10 1 5 10 1 [26] 4 7 10 6 6 7 1 3 5 6 5 1 9 4 5 5 1 1 9 7 6 4 4 5 10 [[7]] [1] 13 2 9 3 18 2 16 4 8 3 7 3 3 2 3 9 15 4 8 14 17 4 15 20 20 [26] 3 4 6 11 6 14 4 15 18 5 9 19 7 3 18 6 2 4 18 3 4 19 15 17 8 [[8]] [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" [20] "T" "U" "V" "W" "X" "Y" "Z" [[9]] [1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 [26] 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50