將列表中的值替換爲數字，然後執行算術計算

Question

這可能相對簡單。我有一個看起來像這樣一個龐大的數據幀：

df1 <- structure(list(place = structure(c(1L, 5L, 1L, 4L), .Label = c("1","2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23","24", "25", "26"), class = "factor"), x = structure(list(c("A", "B", "C", "D", "E"), c("D", "E", "F","G", "H", "I"), c("D", "E", "F", "G", "H"), c("F", "H")), class = "AsIs")), .Names = c("place", "x"), row.names = c(1L, 2L, 3L, 4L), class = "data.frame") 

> df1 
    place   x 
1  1 A, B, C,.... 
2  5 D, E, F,.... 
3  1 D, E, F,.... 
4  4   F, H 

，另一種是對每個列表元素在df1相應的值：

df2 <- structure(list(x = c('A','B','C','D','E','F','G','H','I','J','K','L','M'), value = c("5.2", "1.8", "2.7","3.8", "5.0","3.2", "4.5","2.4", "3.9", "1.2","2.3","4.3", "3.0")), .Names = c("x", "value"), row.names = c(1L,2L,3L,4L,5L,6L,7L,8L,9L,10L, 11L, 12L, 13L), class = "data.frame") 

    x value 
1 A 5.2 
2 B 1.8 
3 C 2.7 
4 D 3.8 
5 E 5.0 
6 F 3.2 
7 G 4.5 
8 H 2.4 
9 I 3.9 
10 J 1.2 
11 K 2.3 
12 L 4.3 
13 M 3.0 

我要替換的元素df1其對應的值爲df2（因此A中的每個df1應該是5.2等等），然後執行操作，例如使用這些值的每個地點的平均值x。謝謝！一步到位

sapply(df1$x, mean) 

或者：

Answer 1

如果數據集較大使用qdap的lookup功能的環境中查找可能使用的：

library(qdap) 
lapply(df1[, 2], lookup, df2) 

或獲得手段

df2$value <- as.numeric(df2$value) #convert your df2 value column to numeric 
sapply(df1[, 2], function(x) mean(lookup(x, df2))) 

Answer 2

您可以使用match和sapply：

df1$x <- sapply(df1$x, function(x) df2$value[match(x, df2$x)]) 

df1$x 
# [[1]] 
# [1] "5.2" "1.8" "2.7" "3.8" "5.0" 
# 
# [[2]] 
# [1] "3.8" "5.0" "3.2" "4.5" "2.4" "3.9" 
# 
# [[3]] 
# [1] "3.8" "5.0" "3.2" "4.5" "2.4" 
# 
# [[4]] 
# [1] "3.2" "2.4" 

---

根據註釋：

爲了平均每行，可以再次使用sapply ：

sapply(df1$x, function(x) mean(df2$value[match(x, df2$x)]))