如何刪除R中特定行中的字符？

Question

如果特定值在V1中，我想將其從下一行的V2列中刪除。

輸入：

         V1               V2
19 49426099      19 49469087
19 49469087      19 49426099
6 29910378       6 29910742 - 6 29911064 - 6 29911086 - 6 29911092 - 6 29911154 
6 29910742       6 29910378 - 6 29911064 - 6 29911086 - 6 29911092 - 6 29911154 
6 29911064       6 29910378 - 6 29910742 - 6 29911086 - 6 29911092 - 6 29911154 

我期望這個結果：

         V1               V2
19 49426099      19 49469087
19 49469087      
6 29910378       6 29910742 - 6 29911064 - 6 29911086 - 6 29911092 - 6 29911154 
6 29910742       6 29911064 - 6 29911086 - 6 29911092 - 6 29911154 
6 29911064       6 29911086 - 6 29911092 - 6 29911154 

Answer 1

這是一個示例數據框：

d = data.frame(V1 = c('19 49426099','19 49469087','6 29910378','6 29910742','6 29911064'), V2 = c('19 49469087','19 49426099','6 29910742 - 6 29911064 - 6 29911086 - 6 29911092 - 6 29911154','6 29910378 - 6 29911064 - 6 29911086 - 6 29911092 - 6 29911154','6 29910378 - 6 29910742 - 6 29911086 - 6 29911092 - 6 29911154'))
d$V1 = as.character(d$V1)
d$V2 = as.character(d$V2)

這是一個解決方案：

r = sapply(0:(nrow(d) - 1), function(i){
gsub(pattern = paste(d[1:i, 'V1'], collapse = '|'),'', x = d[i+1, 'V2'])
})
r = gsub(pattern = ' -  - ', replacement = '', x = r) # remove the gaps where numbers were removed
r = gsub(pattern = '^ - ', replacement = '', x = r) # remove gaps at the beginning
r = gsub(pattern = ' - $', replacement = '', x = r) # in case you have gaps at the end
d$V2 = r