使用两个不同长度的向量迭代循环

Question

我有两个数据框：

harv<-structure(list(spp = c("Other species (please list species name; i.e. Tarpon)", 
"Other species (please list species name; i.e. Amberjack)", "Red Drum (a.k.a. Redfish or Red)", 
"Other species (please list species name; i.e. Tarpon)", "Other species (please list species name; i.e. Amberjack)", 
"Red Drum (a.k.a. Redfish or Red)", "Other species (please list species name; i.e. Tarpon)"
), number = c(1, 2, 2, 4, 5, 7, 9)), class = "data.frame", row.names = c(NA, 
-7L))

oth<-structure(list(spp = c("Tink", "Chii", "Blue", "Red", "Blue")), class = "data.frame", row.names = c(NA, 
-5L))

我想迭代循环，以便每次 spp 名称包含“Other”时，它都会按照

oth

数据框的顺序替换它。这是

harv

数据框的样子：

                                                       spp number
1    Other species (please list species name; i.e. Tarpon)      1
2 Other species (please list species name; i.e. Amberjack)      2
3                         Red Drum (a.k.a. Redfish or Red)      2
4    Other species (please list species name; i.e. Tarpon)      4
5 Other species (please list species name; i.e. Amberjack)      5
6                         Red Drum (a.k.a. Redfish or Red)      7
7    Other species (please list species name; i.e. Tarpon)      9

当我运行这个循环时：

for (i in seq_along(oth$spp)) {
  # Find indices where "Other" is present in spp
  indices <- grep("Other", harv$spp)
  # Replace spp values at the found indices with oth$spp[i]
  harv$spp[indices] <- oth$spp[i]
}

它为我提供了一个数据框，仅提取 oth$spp[i] 向量中的名称

"Tink"

。数据框如下所示：

 spp number
1                             Tink      1
2                             Tink      2
3 Red Drum (a.k.a. Redfish or Red)      2
4                             Tink      4
5                             Tink      5
6 Red Drum (a.k.a. Redfish or Red)      7
7                             Tink      9

如何创建一个循环，以便每个“其他”

harv$spp

依次替换为

oth

向量中的内容？

我想获得一个如下所示的数据框，将每个“其他”替换为

oth

数据框中的内容，顺序与该数据框相同：

spp number
1                             Tink      1
2                             Chii      2
3 Red Drum (a.k.a. Redfish or Red)      2
4                             Blue      4
5                             Red       5
6 Red Drum (a.k.a. Redfish or Red)      7
7                             Blue      9

Answer 1

无需循环——在基 R 中执行此操作所需的函数是向量化，这意味着该函数将对向量的所有元素进行操作，而无需一次循环并作用于每个元素：

idx <- which(startsWith(harv$spp, "Other"))
harv$spp[idx] <- oth$spp[seq_along(idx)]

还要小心在这里使用

grep

，它采用正则表达式来匹配字符串模式（也许这就是您想要做的）。按照您编写的方式，这将与字符串中任何位置的“Other”匹配。