删除list中的部分元素
直接指定要删除的元素为NULL
lts = list(1, 2, 'a', matrix(1:3))
print(length(lts))## [1] 4lts[[3]]## [1] "a"lts[[3]] = NULL
lts[[3]]## [,1]
## [1,] 1
## [2,] 2
## [3,] 3print(length(lts))## [1] 3按照序号/list的name删除，即按照序号或name选择要提取的元素
lts = list(1, 2, 'a', matrix(1:3))
print(length(lts))## [1] 4lts[c(2,4)] = NULL
print(lts)## [[1]]
## [1] 1
##
## [[2]]
## [1] "a"R中操作符皆为函数
具体示例：
`+`(3,2)## [1] 5x = 1:10
`[`(x, 2)## [1] 2`[`(x, -2)## [1] 1 3 4 5 6 7 8 9 10`[<-`(iris[1:2, ], 'new_col_name', value = "future")## Sepal.Length Sepal.Width Petal.Length Petal.Width Species new_col_name
## 1 5.1 3.5 1.4 0.2 setosa future
## 2 4.9 3.0 1.4 0.2 setosa futureapply类函数中使用符号函数
lapply提取元素指定的列
当list中的元素为data.frame/matrix，需要提取其中的指定列
lts = split(subset(iris, select = -Species), iris$Species)
str(lts)## List of 3
## $ setosa :'data.frame': 50 obs. of 4 variables:
## ..$ Sepal.Length: num [1:50] 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
## ..$ Sepal.Width : num [1:50] 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
## ..$ Petal.Length: num [1:50] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ...
## ..$ Petal.Width : num [1:50] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ...
## $ versicolor:'data.frame': 50 obs. of 4 variables:
## ..$ Sepal.Length: num [1:50] 7 6.4 6.9 5.5 6.5 5.7 6.3 4.9 6.6 5.2 ...
## ..$ Sepal.Width : num [1:50] 3.2 3.2 3.1 2.3 2.8 2.8 3.3 2.4 2.9 2.7 ...
## ..$ Petal.Length: num [1:50] 4.7 4.5 4.9 4 4.6 4.5 4.7 3.3 4.6 3.9 ...
## ..$ Petal.Width : num [1:50] 1.4 1.5 1.5 1.3 1.5 1.3 1.6 1 1.3 1.4 ...
## $ virginica :'data.frame': 50 obs. of 4 variables:
## ..$ Sepal.Length: num [1:50] 6.3 5.8 7.1 6.3 6.5 7.6 4.9 7.3 6.7 7.2 ...
## ..$ Sepal.Width : num [1:50] 3.3 2.7 3 2.9 3 3 2.5 2.9 2.5 3.6 ...
## ..$ Petal.Length: num [1:50] 6 5.1 5.9 5.6 5.8 6.6 4.5 6.3 5.8 6.1 ...
## ..$ Petal.Width : num [1:50] 2.5 1.9 2.1 1.8 2.2 2.1 1.7 1.8 1.8 2.5 ...# 提取每个list中的1/2列
lts_sel <- lapply(lts, "[", 1:2)
str(lts_sel)## List of 3
## $ setosa :'data.frame': 50 obs. of 2 variables:
## ..$ Sepal.Length: num [1:50] 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
## ..$ Sepal.Width : num [1:50] 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
## $ versicolor:'data.frame': 50 obs. of 2 variables:
## ..$ Sepal.Length: num [1:50] 7 6.4 6.9 5.5 6.5 5.7 6.3 4.9 6.6 5.2 ...
## ..$ Sepal.Width : num [1:50] 3.2 3.2 3.1 2.3 2.8 2.8 3.3 2.4 2.9 2.7 ...
## $ virginica :'data.frame': 50 obs. of 2 variables:
## ..$ Sepal.Length: num [1:50] 6.3 5.8 7.1 6.3 6.5 7.6 4.9 7.3 6.7 7.2 ...
## ..$ Sepal.Width : num [1:50] 3.3 2.7 3 2.9 3 3 2.5 2.9 2.5 3.6 ...# 提取每个list中的1/2行
lts_sel <- lapply(lts, "[", 1:2, )
lts_sel## $setosa
## Sepal.Length Sepal.Width Petal.Length Petal.Width
## 1 5.1 3.5 1.4 0.2
## 2 4.9 3.0 1.4 0.2
##
## $versicolor
## Sepal.Length Sepal.Width Petal.Length Petal.Width
## 51 7.0 3.2 4.7 1.4
## 52 6.4 3.2 4.5 1.5
##
## $virginica
## Sepal.Length Sepal.Width Petal.Length Petal.Width
## 101 6.3 3.3 6.0 2.5
## 102 5.8 2.7 5.1 1.9# 提取每个list中的1:2行/1:2列
lts_sel <- lapply(lts, "[", 1:2, 1:2)
lts_sel## $setosa
## Sepal.Length Sepal.Width
## 1 5.1 3.5
## 2 4.9 3.0
##
## $versicolor
## Sepal.Length Sepal.Width
## 51 7.0 3.2
## 52 6.4 3.2
##
## $virginica
## Sepal.Length Sepal.Width
## 101 6.3 3.3
## 102 5.8 2.7# 提取每个list中的1:2行/1列
lts_sel <- lapply(lts, "[", 1:2, 1, drop = F)
lts_sel## $setosa
## Sepal.Length
## 1 5.1
## 2 4.9
##
## $versicolor
## Sepal.Length
## 51 7.0
## 52 6.4
##
## $virginica
## Sepal.Length
## 101 6.3
## 102 5.8mapply给list添加多余列
lts = split(subset(iris, select = -Species), iris$Species)
lts <- lapply(lts, "[", 1:2, 1:2)
lts## $setosa
## Sepal.Length Sepal.Width
## 1 5.1 3.5
## 2 4.9 3.0
##
## $versicolor
## Sepal.Length Sepal.Width
## 51 7.0 3.2
## 52 6.4 3.2
##
## $virginica
## Sepal.Length Sepal.Width
## 101 6.3 3.3
## 102 5.8 2.7lts_cols = mapply(`[<-`, lts, 'Species', value = names(lts), SIMPLIFY = FALSE)
lts_cols## $setosa
## Sepal.Length Sepal.Width Species
## 1 5.1 3.5 setosa
## 2 4.9 3.0 setosa
##
## $versicolor
## Sepal.Length Sepal.Width Species
## 51 7.0 3.2 versicolor
## 52 6.4 3.2 versicolor
##
## $virginica
## Sepal.Length Sepal.Width Species
## 101 6.3 3.3 virginica
## 102 5.8 2.7 virginicalts_cols = mapply(`[<-`, lts, paste0('Species', 1:3), value = names(lts), SIMPLIFY = FALSE)
lts_cols## $setosa
## Sepal.Length Sepal.Width Species1
## 1 5.1 3.5 setosa
## 2 4.9 3.0 setosa
##
## $versicolor
## Sepal.Length Sepal.Width Species2
## 51 7.0 3.2 versicolor
## 52 6.4 3.2 versicolor
##
## $virginica
## Sepal.Length Sepal.Width Species3
## 101 6.3 3.3 virginica
## 102 5.8 2.7 virginicalist合并为dataframe
lts_cols = mapply(`[<-`, lts, 'Species', value = names(lts), SIMPLIFY = FALSE)
do.call("rbind", lts_cols)## Sepal.Length Sepal.Width Species
## setosa.1 5.1 3.5 setosa
## setosa.2 4.9 3.0 setosa
## versicolor.51 7.0 3.2 versicolor
## versicolor.52 6.4 3.2 versicolor
## virginica.101 6.3 3.3 virginica
## virginica.102 5.8 2.7 virginicalts_cols = mapply(`[<-`, lts, paste0('Species', 1:3), value = names(lts), SIMPLIFY = FALSE)
dplyr::bind_rows(lts_cols)## Sepal.Length Sepal.Width Species1 Species2 Species3
## 1 5.1 3.5 setosa <NA> <NA>
## 2 4.9 3.0 setosa <NA> <NA>
## 3 7.0 3.2 <NA> versicolor <NA>
## 4 6.4 3.2 <NA> versicolor <NA>
## 5 6.3 3.3 <NA> <NA> virginica
## 6 5.8 2.7 <NA> <NA> virginica