将多行转换为单列

Question

我使用的是R，我想将DataFrame-1转换为DataFrame-2

DataFrame-1
Variable1     Variable2
aa1           X1
aa1           Y2
aa1           Z1 
bb1           Y1
bb1           Y2 

我想要创建DataFrame-2，它将如下所示

Variable1     Variable2
aa1           X1, Y2, Z1
bb1           Y1, Y2

Answer 1

dat <- data.frame(Var1 = c("aa1", "aa1", "aa1", "bb1", "bb1"), Var2 = c("X1", "Y2", "Z1", "Y1", "Y2"), stringsAsFactors = FALSE)

cbind(Var1 = unique(dat$Var1), 
      Var2 = sapply(unique(dat$Var1), function(x) paste0(dat$Var2[dat$Var1 == x], collapse = ", "), USE.NAMES = F))

     Var1  Var2        
[1,] "aa1" "X1, Y2, Z1"
[2,] "bb1" "Y1, Y2" 

Answer 2

library(dplyr)

df1 <- df %>%
  group_by(Variable1) %>%
  summarise(Variable2 = paste(Variable2, collapse = ", ")) %>%
  data.frame()
df1

产出如下：

  Variable1  Variable2
1       aa1 X1, Y2, Z1
2       bb1     Y1, Y2

样本数据：

df <- structure(list(Variable1 = c("aa1", "aa1", "aa1", "bb1", "bb1"
), Variable2 = c("X1", "Y2", "Z1", "Y1", "Y2")), .Names = c("Variable1", 
"Variable2"), class = "data.frame", row.names = c(NA, -5L))

Answer 3

这是cars数据集的一个示例：

split <- split(cars$dist, cars$speed)  

a <- list(length(split))
for (i in 1:length(split)){

  a[i] = paste(split[[i]], sep = "", collapse = ", ")}

df <- data.frame(x = labels(split), y = unlist(a))

输出将如下所示：

    x                  y
1   4              2, 10
2   7              4, 22
3   8                 16
4   9                 10
5  10         18, 26, 34
6  11             17, 28
7  12     14, 20, 24, 28
8  13     26, 34, 34, 46
9  14     26, 36, 60, 80
10 15         20, 26, 54
11 16             32, 40
12 17         32, 40, 50
13 18     42, 56, 76, 84
14 19         36, 46, 68
15 20 32, 48, 52, 56, 64
16 22                 66
17 23                 54
18 24    70, 92, 93, 120
19 25                 85