R将分隔整数映射到分隔字符串

Question

输入

我有以下数据框（标题到期和水果）。

我有以下向量：

index <- c("apple", "kiwi", "banana", "peach", "grape")

其中苹果 = 1，猕猴桃 = 2，香蕉 = 3，桃子 = 4，葡萄 = 5

输出

我想得到以下输出。

我该如何解决这个问题？

数据来源

myDf <- structure(list(expiry = 20161212:20161215, fruit = structure(c(4L, 
1L, 2L, 3L), .Label = c("2,4", "3,2", "4", "5,3,1"), class = "factor")), .Names = c("expiry", 
"fruit"), class = "data.frame", row.names = c(NA, -4L))


index <- c("apple", "kiwi", "banana", "peach", "grape")

Answer 1

在 tidyverse 中更具可读性：

library(dplyr)
library(purrr)

df <- data_frame(expiry=c("20161212", "20161213", "20161214", "20161215"),
                 fruit=c("5,3,1", "2,4", "3,2", 4))

index <- c("apple", "kiwi", "banana", "peach", "grape")

by_row(df, function(x) {

  strsplit(x$fruit, ",")[[1]] %>%
    as.numeric() %>%
    map_chr(~index[.]) %>%
    paste0(collapse=",")

}, .collate="cols", .to="fruit_names") %>%
  select(expiry, fruit=fruit_names)
## # A tibble: 4 × 2
##     expiry              fruit
##      <chr>              <chr>
## 1 20161212 grape,banana,apple
## 2 20161213         kiwi,peach
## 3 20161214        banana,kiwi
## 4 20161215              peach

Answer 2

您可以使用sapply、strsplit 和as.numeric、as.character 来创建变量：

myDf$fruit2 <- sapply(as.character(myDf$fruit), function(x) 
  paste0(index[as.numeric(strsplit(x, split = ",")[[1]])], collapse = ", "))