我想从下面的数组中删除 & 和 . 并只提取数字，

x = as.factor(c(".&.", "0.0119885482338&.&.", ".&2.25880593895", ".&.&.&.&.&.&.&.", ".&0.295142083575&.", "0.708323350364",".&.&0.193766679861",".&.&.&.&7.65239874523E-4&.&."))

我尝试了以下 gsub() 命令:

gsub("[^0-9.E-]","",x)

输出:

".."                     "0.0119885482338.."      ".2.25880593895"         
"........"              
".0.295142083575."       "0.708323350364"         "..0.193766679861"       
"....7.65239874523E-4.." 

更新上述 gsub 命令的任何建议，以便输出如下所示:

"" "0.0119885482338" "2.25880593895" "" "0.295142083575" 
"0.708323350364" "0.193766679861" "7.65239874523E-4"  

最佳答案

你可以使用

> sub("^.*?(?:([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?).*|$)","\\1",x)
[1] ""                 "0.0119885482338"  "2.25880593895"    ""                 "0.295142083575"   "0.708323350364"   "0.193766679861"   "7.65239874523E-4"

参见 regex demo .

详细信息:

• ^ - 字符串的开始
• .*? - 任何文本，尽可能短
• (?: - 非捕获组的开始:
  • ([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?) - 第 1 组(\1): number pattern
  • .* - 字符串的其余部分
• |
  • $ - 字符串结尾
• ) - 非捕获组结束。

查看 online R demo :

x=as.factor(c(".&.", "0.0119885482338&.&.", ".&2.25880593895", ".&.&.&.&.&.&.&.", ".&0.295142083575&.", "0.708323350364",".&.&0.193766679861",".&.&.&.&7.65239874523E-4&.&."))
sub("^.*?(?:([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?).*|$)","\\1",x)
## => [1] ""                 "0.0119885482338"  "2.25880593895"    ""                
##    [5] "0.295142083575"   "0.708323350364"   "0.193766679861"   "7.65239874523E-4"

https://stackoverflow.com/questions/67456482/