Question

我有一个如下所示的CSV文件：

a, b, c, d
e, f

我想将行旋转看起来像一个矩阵。将每个项目排在第一行，同一行中的所有其他项目排在第一位。

a, b, c, d
b, c, d, a
c, d, a, b
d, a, b, c     
e, f
f, e

有关如何在Java或R中实现此功能的建议？

Answer 1

以下是使用sapply和子集化的第一行的方法：

vec <- letters[1:4]

sapply(1:4, function(i) vec[c(i:4, 1:i)][1:4])
     [,1] [,2] [,3] [,4]
[1,] "a"  "b"  "c"  "d" 
[2,] "b"  "c"  "d"  "a" 
[3,] "c"  "d"  "a"  "b" 
[4,] "d"  "a"  "b"  "c"

R中最简单的方法是使用列表，因为每行中的元素数量不同。使用列表结构，这是一个嵌套的sapply方法：

myList <- list(letter[1:4], letters[5:6])
sapply(myList, function(j) {
                 sapply(1:length(j), function(i) {
                   j[c(i:length(j), 1:i)][1:length(j)]})})
[[1]]
     [,1] [,2] [,3] [,4]
[1,] "a"  "b"  "c"  "d" 
[2,] "b"  "c"  "d"  "a" 
[3,] "c"  "d"  "a"  "b" 
[4,] "d"  "a"  "b"  "c" 

[[2]]
     [,1] [,2]
[1,] "e"  "f" 
[2,] "f"  "e"

Answer 2

在R中，我们可以遍历行并使用matrix来获得预期的输出

lst <- apply(df, 1, function(x)  {x1 <-x[nzchar(x)]
        head(matrix(x1, nrow=length(x1)+1, ncol = length(x1)),-1)})
lst
#[[1]]
#    [,1] [,2] [,3] [,4]
#[1,] "a"  "b"  "c"  "d" 
#[2,] "b"  "c"  "d"  "a" 
#[3,] "c"  "d"  "a"  "b" 
#[4,] "d"  "a"  "b"  "c" 

#[[2]]
#    [,1] [,2]
#[1,] "e"  "f" 
#[2,] "f"  "e"

注意：如果我们有NA而不是空白（''），请在上面的代码中使用x1 <- x[!is.na(x)]。

如果我们需要创建单个数据集，则可以使用rbindlist中的data.table

library(data.table)
rbindlist(lapply(lst, as.data.frame), fill = TRUE)
#   V1 V2 V3 V4
#1:  a  b  c  d
#2:  b  c  d  a
#3:  c  d  a  b
#4:  d  a  b  c
#5:  e  f NA NA
#6:  f  e NA NA

数据

df <- structure(list(v1 = c("a", "e"), v2 = c("b", "f"), v3 = c("c", 
""), v4 = c("d", "")), .Names = c("v1", "v2", "v3", "v4"),
 row.names = c(NA, -2L), class = "data.frame")

转换/旋转CSV

2 个答案:

数据