根据 R 中的列值将数据框重新排列为矩阵？ [复制]

Question

我有一个包含三列的数据框：值、类型和类。

看起来像这样：

df = data.frame(value = c(1:10), type = c("a","b","c","a","b","b","c","a","b","b"), 
                 class = c("aos","aos","ezx","ezx","kl","kl","wq","wq","us","us"))

    
value  type class
    1   a   aos
    2   b   aos
    3   c   ezx
    4   a   ezx
    5   b   kl
    6   b   kl
    7   c   wq
    8   a   wq
    9   b   us
    10  b   us

我想将它重新排列成一个矩阵，其中列代表不同的类型值，行代表类值，相交的值是数据帧中原始数据的平均值。

我正在寻找的矩阵应该是这样的：

   aos   ezx    kl   wq     us

a    1     4          8
b    2         5.5         9.5
c          3          7

Answer 1

我们可以使用tapply from base R 来返回结构体

with(df, tapply(value, list(type, class), FUN = mean))
#  aos ezx  kl  us wq
#a   1   4  NA  NA  8
#b   2  NA 5.5 9.5 NA
#c  NA   3  NA  NA  7

---

或者与pivot_wider一起使用values_fn

library(tidyr)
library(dplyr)
library(tibble)
df %>% 
  pivot_wider(names_from = class, values_from = value, values_fn = mean) %>% 
  column_to_rownames('type') %>%
   as.matrix
#  aos ezx  kl wq  us
#a   1   4  NA  8  NA
#b   2  NA 5.5 NA 9.5
#c  NA   3  NA  7  NA