对于r中的循环问题:if(length [i] == 1){中的错误:缺少需要TRUE/FALSE的值 [英] For loop problems in r: Error in if (length[i] == 1) { : missing value where TRUE/FALSE needed

问题描述

ann <- 1:2500
len <- sample(1:3,1000,replace=TRUE)
df <- data.frame(col1= c(1:2500),col2= c(1:2500))

for (i in 1:length(ann)) {
      if (length[i]==1) { 
            df$col1[i] <- len[i] }
      else if (length[i]==2) { 
            df$col1[i] <- len[i] 
            df$col1[i+1] <- len[i] }
      else if (length[i]==3) {  
            df$col1[i] <- len[i]
            df$col1[i+1] <- len[i]
            df$col1[i+2] <- len[i] }
}

试图在下一行用数字2重复2的每个实例.而且，如果有3，我希望此后的两行都用数字3.谢谢！我需要练习for循环.

Trying to make every instance of a 2 to be repeated on the following line with the number 2. Also, if there is a 3, I want the two lines following this to have the number 3. Thanks! I need practice with for loops.

Error in if (length[i] == 1) { : missing value where TRUE/FALSE needed

更新:for循环将用以下数字替换每个重复的行，我需要知道如何使2的每个实例之后的i + 1和3的每个实例之后的i + 2.

Update: The for loop will replace every repeated row with the following numbers, I need to know how to make i+1 after every instance of a 2, and i+2 after every instance of a 3.

推荐答案

在这里，我们可以遍历len的所有元素，并为每个循环做一个内部循环，将len的元素输入其中. df$col1的许多行.

Here we can iterate through all the elements of len, and for each do an inner loop that takes that element of len and enters it into that many rows of df$col1.

df_row <- 1
for (i in 1:length(len)) {
  for (j in 1:len[i]) {
    df[df_row, 1] = len[i]
    df_row <- df_row + 1
  }
}

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