r - 矩阵中两个字符串的最大 nchar

Question

我想找到更好的方法来找到我正在相互比较的两个字符串的更大 nchar。

假设我在 sentenceMatch data.frame 中有字符串，我需要创建一个 max(nchar(string1), nchar(string2)) 矩阵，但没有 for 循环，这是非常慢的方法。

sentenceMatch <- data.frame(Sentence=c("hello how are you",
                                   "hello how are you friend",
                                   "im fine and how about you",
                                   "good thanks",
                                   "great to hear that"))

sentenceMatch$Sentence <- as.character(sentenceMatch$Sentence)

overallMatrix_nchar <- matrix(, nrow = dim(sentenceMatch)[1], ncol = dim(sentenceMatch)[1])

for (k in 1:dim(sentenceMatch)[1]) {
  for (l in 1:dim(sentenceMatch)[1]) {
    overallMatrix_nchar[k, l] <- max(nchar(sentenceMatch[k, ]), nchar(sentenceMatch[l, ]))
  }
}

有没有更好的解决方案如何加快这个计算？非常感谢您对前进的任何帮助。

Answer 1

使用 outer :

nc <- nchar(sentenceMatch[[1]])
outer(nc, nc, pmax)

给予:

     [,1] [,2] [,3] [,4] [,5]
[1,]   17   24   25   17   18
[2,]   24   24   25   24   24
[3,]   25   25   25   25   25
[4,]   17   24   25   11   18
[5,]   18   24   25   18   18