Question

我要替换的for循环末尾的长度为零。好的，我知道此错误表示NULL或长度为0的向量。我尝试了一些解决方案，但都无济于事。如何从na / 0结果中转义并继续循环？

for(i in 1:nrow(df)){
  df[i,3] <- ... #that doesn't matter
  if(length(df[i,3] == 0)){
    df[i,3] <- "Not found"
  }
}

Error in x[[jj]][iseq] <- vjj : replacement has length zero

或

for(i in 1:nrow(df)){
  df[i,3] <- ... #that doesn't matter
  if(is.na(df[i,3] == TRUE){
    df[i,3] <- "Not found"
  }
}

Error in x[[jj]][iseq] <- vjj : replacement has length zero

谢谢。

编辑：示例：

column1      column2          column3
   a      www.example.com/a     100
   b      www.example.com/b     150
   c      www.example.com/c     NA
   d      www.example.com/d     NA

以此类推...我的目标是跳过它找不到的链接（c），并保持循环运行。

Answer 1

为何不使用for循环来转换列，为什么不使用dplyr :: mutate函数？

library(dplyr)

testFrame <- data.frame(a = 1:5, b = c(0,1,1,NA,0))

testFrameEdited <- testFrame %>% 
  mutate(b = ifelse(b == 0 | is.na(b), 'Not found', b))

testFrameEdited

返回

  a         b
1 1 Not found
2 2         1
3 3         1
4 4 Not found
5 5 Not found

For循环-如何克服R中长度为零的替换问题？

1 个答案: