如何删除R中向量的某些最后元素？
R中的向量可以具有无限数量的元素，但是我们可能希望删除其中的一些元素。要删除向量的最后一个元素，我们可以将head函数与不需要的值的数量带负号一起使用。例如，如果我们有一个长度为200的向量，但我们不希望最后50个元素，那么可以使用head(vector_name,-50)。
例子
x1<-rnorm(100) x1
输出结果
[1] 0.19166338 1.55254427 0.91424229 0.35862537 0.17509564 -0.84726777 [7] 0.97823166 1.80586826 0.12291480 -0.12977203 -0.21642866 1.44647817 [13] 0.40970980 0.91091657 1.43035817 -0.38129196 0.20230718 -0.80619919 [19] 0.29463418 1.40488308 1.02376685 0.47612606 -0.67033033 0.15923432 [25] -0.38271538 0.93576259 -0.63153227 -0.09830608 1.03198498 0.38780843 [31] -1.25612931 -0.78695273 0.42981155 -0.37641622 -1.21622907 1.02927851 [37] 0.43039700 -1.24557402 -0.60272849 0.66006939 2.05074953 0.49080818 [43] -1.73147942 0.71088366 0.01382291 -1.40104160 1.25912367 -0.12747752 [49] -0.72938651 -1.21136136 0.59961974 -1.16032953 0.43909343 0.20485374 [55] -0.69918134 -0.92662568 -1.01348238 0.60498706 1.73440013 -0.34985053 [61] 1.19918551 1.02390100 -0.04627515 1.38650843 -2.19527272 -0.12755691 [67] -1.31699684 -1.42693514 0.87944163 0.39399158 0.68892548 2.35371650 [73] -1.01509767 0.29097752 1.56532608 -0.84711837 1.32766016 0.47704633 [79] 0.18525094 0.25329489 2.59222735 1.07434699 -1.59690189 -0.08758860 [85] 0.36076759 -0.87995998 -3.32333496 -0.46751545 0.43154027 -0.60398945 [91] 0.67444669 0.63592054 -0.61297039 0.41489135 0.87734337 0.02115758 [97] 1.81038329 -0.45209570 -0.12512399 0.76680042
示例
head(x1,-50)
输出结果
[1] 0.19166338 1.55254427 0.91424229 0.35862537 0.17509564 -0.84726777 [7] 0.97823166 1.80586826 0.12291480 -0.12977203 -0.21642866 1.44647817 [13] 0.40970980 0.91091657 1.43035817 -0.38129196 0.20230718 -0.80619919 [19] 0.29463418 1.40488308 1.02376685 0.47612606 -0.67033033 0.15923432 [25] -0.38271538 0.93576259 -0.63153227 -0.09830608 1.03198498 0.38780843 [31] -1.25612931 -0.78695273 0.42981155 -0.37641622 -1.21622907 1.02927851 [37] 0.43039700 -1.24557402 -0.60272849 0.66006939 2.05074953 0.49080818 [43] -1.73147942 0.71088366 0.01382291 -1.40104160 1.25912367 -0.12747752 [49] -0.72938651 -1.21136136
示例
head(x1,-10)
输出结果
[1] 0.19166338 1.55254427 0.91424229 0.35862537 0.17509564 -0.84726777 [7] 0.97823166 1.80586826 0.12291480 -0.12977203 -0.21642866 1.44647817 [13] 0.40970980 0.91091657 1.43035817 -0.38129196 0.20230718 -0.80619919 [19] 0.29463418 1.40488308 1.02376685 0.47612606 -0.67033033 0.15923432 [25] -0.38271538 0.93576259 -0.63153227 -0.09830608 1.03198498 0.38780843 [31] -1.25612931 -0.78695273 0.42981155 -0.37641622 -1.21622907 1.02927851 [37] 0.43039700 -1.24557402 -0.60272849 0.66006939 2.05074953 0.49080818 [43] -1.73147942 0.71088366 0.01382291 -1.40104160 1.25912367 -0.12747752 [49] -0.72938651 -1.21136136 0.59961974 -1.16032953 0.43909343 0.20485374 [55] -0.69918134 -0.92662568 -1.01348238 0.60498706 1.73440013 -0.34985053 [61] 1.19918551 1.02390100 -0.04627515 1.38650843 -2.19527272 -0.12755691 [67] -1.31699684 -1.42693514 0.87944163 0.39399158 0.68892548 2.35371650 [73] -1.01509767 0.29097752 1.56532608 -0.84711837 1.32766016 0.47704633 [79] 0.18525094 0.25329489 2.59222735 1.07434699 -1.59690189 -0.08758860 [85] 0.36076759 -0.87995998 -3.32333496 -0.46751545 0.43154027 -0.60398945
示例
head(x1,-90)
输出结果
[1] 0.1916634 1.5525443 0.9142423 0.3586254 0.1750956 -0.8472678 [7] 0.9782317 1.8058683 0.1229148 -0.1297720
示例
head(x1,-30)
输出结果
[1] 0.19166338 1.55254427 0.91424229 0.35862537 0.17509564 -0.84726777 [7] 0.97823166 1.80586826 0.12291480 -0.12977203 -0.21642866 1.44647817 [13] 0.40970980 0.91091657 1.43035817 -0.38129196 0.20230718 -0.80619919 [19] 0.29463418 1.40488308 1.02376685 0.47612606 -0.67033033 0.15923432 [25] -0.38271538 0.93576259 -0.63153227 -0.09830608 1.03198498 0.38780843 [31] -1.25612931 -0.78695273 0.42981155 -0.37641622 -1.21622907 1.02927851 [37] 0.43039700 -1.24557402 -0.60272849 0.66006939 2.05074953 0.49080818 [43] -1.73147942 0.71088366 0.01382291 -1.40104160 1.25912367 -0.12747752 [49] -0.72938651 -1.21136136 0.59961974 -1.16032953 0.43909343 0.20485374 [55] -0.69918134 -0.92662568 -1.01348238 0.60498706 1.73440013 -0.34985053 [61] 1.19918551 1.02390100 -0.04627515 1.38650843 -2.19527272 -0.12755691 [67] -1.31699684 -1.42693514 0.87944163 0.39399158
示例
head(x1,-20)
输出结果
[1] 0.19166338 1.55254427 0.91424229 0.35862537 0.17509564 -0.84726777 [7] 0.97823166 1.80586826 0.12291480 -0.12977203 -0.21642866 1.44647817 [13] 0.40970980 0.91091657 1.43035817 -0.38129196 0.20230718 -0.80619919 [19] 0.29463418 1.40488308 1.02376685 0.47612606 -0.67033033 0.15923432 [25] -0.38271538 0.93576259 -0.63153227 -0.09830608 1.03198498 0.38780843 [31] -1.25612931 -0.78695273 0.42981155 -0.37641622 -1.21622907 1.02927851 [37] 0.43039700 -1.24557402 -0.60272849 0.66006939 2.05074953 0.49080818 [43] -1.73147942 0.71088366 0.01382291 -1.40104160 1.25912367 -0.12747752 [49] -0.72938651 -1.21136136 0.59961974 -1.16032953 0.43909343 0.20485374 [55] -0.69918134 -0.92662568 -1.01348238 0.60498706 1.73440013 -0.34985053 [61] 1.19918551 1.02390100 -0.04627515 1.38650843 -2.19527272 -0.12755691 [67] -1.31699684 -1.42693514 0.87944163 0.39399158 0.68892548 2.35371650 [73] -1.01509767 0.29097752 1.56532608 -0.84711837 1.32766016 0.47704633 [79] 0.18525094 0.25329489
示例
head(x1,-80)
输出结果
[1] 0.1916634 1.5525443 0.9142423 0.3586254 0.1750956 -0.8472678 [7] 0.9782317 1.8058683 0.1229148 -0.1297720 -0.2164287 1.4464782 [13] 0.4097098 0.9109166 1.4303582 -0.3812920 0.2023072 -0.8061992 [19] 0.2946342 1.4048831
示例
head(x1,-95)
输出结果
[1] 0.1916634 1.5525443 0.9142423 0.3586254 0.1750956
示例
head(x1,-99)
输出结果
[1] 0.1916634
示例
head(x1,-45)
输出结果
[1] 0.19166338 1.55254427 0.91424229 0.35862537 0.17509564 -0.84726777 [7] 0.97823166 1.80586826 0.12291480 -0.12977203 -0.21642866 1.44647817 [13] 0.40970980 0.91091657 1.43035817 -0.38129196 0.20230718 -0.80619919 [19] 0.29463418 1.40488308 1.02376685 0.47612606 -0.67033033 0.15923432 [25] -0.38271538 0.93576259 -0.63153227 -0.09830608 1.03198498 0.38780843 [31] -1.25612931 -0.78695273 0.42981155 -0.37641622 -1.21622907 1.02927851 [37] 0.43039700 -1.24557402 -0.60272849 0.66006939 2.05074953 0.49080818 [43] -1.73147942 0.71088366 0.01382291 -1.40104160 1.25912367 -0.12747752 [49] -0.72938651 -1.21136136 0.59961974 -1.16032953 0.43909343 0.20485374 [55] -0.69918134
示例
x2 <-LETTERS[1:26] x2
输出结果
[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"
示例
head(x2,-6)
输出结果
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" [20] "T"
示例
head(x2,-20)
输出结果
[1] "A" "B" "C" "D" "E" "F"