比较两列并确定R中的字符差异

Question

I am trying to write a program that examines two columns of text and identifies single errors. For example:

 1    2  
bat  bad  
tap  ta  
tap  tape  

I would like the program to compare column one against column two, and to print the character difference.

Answer 1

Here's an approach using the stringdist package.

# Your data sample, plus a couple of extra rows
dat = data.frame(x=c(1,'bat','tap','tap','tapes','tapped'), 
                 y=c(2,'bad','ta','tape','tapes','tapas'))

dat
       x     y
1      1     2
2    bat   bad
3    tap    ta
4    tap  tape
5  tapes tapes
6 tapped tapas

library(stringdist)

# Distance methods available in stringdist
dist.methods = c("osa", "lv", "dl", "hamming", "lcs", "qgram",
                 "cosine", "jaccard", "jw", "soundex")

# Try all the methods with the sample data
sapply(dist.methods, function(m) stringdist(dat[,1],dat[,2], method=m))

  osa lv dl hamming lcs qgram cosine jaccard jw soundex [1,] 1 1 1 1 2 2 1.0000000 1.0000000 1.00000000 1 [2,] 1 1 1 1 2 2 0.3333333 0.5000000 0.22222222 0 [3,] 1 1 1 Inf 1 1 0.1835034 0.3333333 0.11111111 1 [4,] 1 1 1 Inf 1 1 0.1339746 0.2500000 0.08333333 0 [5,] 0 0 0 0 0 0 0.0000000 0.0000000 0.00000000 0 [6,] 3 3 3 Inf 5 5 0.3318469 0.5000000 0.30000000 1 

Or, using adist , as suggested by @thelatemail:

apply(dat, 1, function(d) adist(d[1], d[2]))

 [1] 1 1 1 1 0 3 

adist uses the Levenshtein distance, equivalent to the lv method above. This is probably the method you want.

For explanations of the different distance methods, see this web page .

Answer 2

here is the code, i think this is you are expecting.

df
  one  two
  bat  bad
  tap   ta
  tap tape

getDiff<-function(dataframe){
  result<-" "
  for(i in 1:nrow(dataframe))

    str1<-unlist(strsplit(dataframe[i,"one"],split = ""))
    str2<-unlist(strsplit(dataframe[i,"two"],split = ""))
    for(j in 1:length(str1)){
      if(j <= length(str2) & str1[j] == str2[j]){
        retstr<-str1[(j+1):length(str1)]
      }else{
        break
      }
    }
    result[i]<-paste(retstr,collapse = "")
  }
  return(result)
}

getDiff(df)


results:
 "t" "p" "" 

i don't know if is there any default function to do this... may be this will be helpful...