我的 for 循环有什么问题？ -gsub 行名

Question

我想遍历所有行并重命名它们。基本上我只想删除我的数据框中的一些单词（每行名称中的相同模式）。

代码：

for (i in rownames(df)) {

  row.names(df)[i] <- gsub("*The words I want to remove*", "", row.names(df)[i])
}

我收到以下错误：

Error in row.names<-.data.frame(*tmp*, value = c("The words I want to remove", : invalid 'row.names' length

请注意，代码在循环外运行良好。

Answer 1

你的序列不好：

在这里，rownames(df) 中的 i 依次是您的每个行名：

for (i in rownames(mtcars)) {
+   print(i)
+ }
[1] "Mazda RX4"
[1] "Mazda RX4 Wag"
[1] "Datsun 710"
...

所以 row.names(df)[i] 正在尝试做 row.names(df)["yourrowname"] 即：row.names(mtcars)["Mazda RX4"] 其中 return 不适用。

按照您编写代码的方式，i 必须是一个数字。所以：

for (i in seq_along(rownames(df))) {
  print(i)
}
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
...

现在，要替换行名称，您需要用双括号将 i 括起来。这是 mtcars 的示例：

data("mtcars")
rownames(mtcars)
[1] "Mazda RX4"           "Mazda RX4 Wag"      
[3] "Datsun 710"          "Hornet 4 Drive"     
[5] "Hornet Sportabout"   "Valiant"            
[7] "Duster 360"          "Merc 240D"          
[9] "Merc 230"            "Merc 280"           
[11] "Merc 280C"           "Merc 450SE"         
[13] "Merc 450SL"          "Merc 450SLC"        
[15] "Cadillac Fleetwood"  "Lincoln Continental"

for (i in seq_along(rownames(mtcars))) {

  row.names(mtcars)[[i]] <- gsub(" ", "_", row.names(mtcars)[[i]])
}
rownames(mtcars)

[1] "Mazda_RX4"           "Mazda_RX4_Wag"      
[3] "Datsun_710"          "Hornet_4_Drive"     
[5] "Hornet_Sportabout"   "Valiant"            
[7] "Duster_360"          "Merc_240D"          
[9] "Merc_230"            "Merc_280"           
[11] "Merc_280C"           "Merc_450SE"         
[13] "Merc_450SL"          "Merc_450SLC"

但是正如评论中所述，您不需要 for 循环：

rownames(mtcars) <- gsub(" ", "_", row.names(mtcars))
rownames(mtcars)
[1] "Mazda_RX4"           "Mazda_RX4_Wag"      
[3] "Datsun_710"          "Hornet_4_Drive"     
[5] "Hornet_Sportabout"   "Valiant"            
[7] "Duster_360"          "Merc_240D"          
[9] "Merc_230"            "Merc_280"           
[11] "Merc_280C"           "Merc_450SE"         
[13] "Merc_450SL"          "Merc_450SLC"

我的 for 循环有什么问题？ -gsub 行名

What is wrong with my for-loop? -gsub rownames

for-loop

r

gsub

dataframe

rowname