Crayon Constantinople Crayon Constantinople - 2 months ago 67
R Question

in R, use gsub to remove all punctuation except period

I am new to R so I hope you can help me.

I want to use gsub to remove all punctuation except for periods and minus signs so I can keep decimal points and negative symbols in my data.

Example

My data frame z has the following data:

[,1] [,2]
[1,] "1" "6"
[2,] "2@" "7.235"
[3,] "3" "8"
[4,] "4" "$9"
[5,] "£5" "-10"


I want to use
gsub("[[:punct:]]", "", z)
to remove the punctuation.

Current output

> gsub("[[:punct:]]", "", z)
[,1] [,2]
[1,] "1" "6"
[2,] "2" "7235"
[3,] "3" "8"
[4,] "4" "9"
[5,] "5" "10"


I would like, however, to keep the "-" sign and the "." sign.

Desired output

PSEUDO CODE:
> gsub("[[:punct:]]", "", z, except(".", "-") )
[,1] [,2]
[1,] "1" "6"
[2,] "2" "7.235"
[3,] "3" "8"
[4,] "4" "9"
[5,] "5" "-10"


Any ideas how I can make some characters exempt from the gsub() function?

Answer

You can put back some matches like this:

 sub("([.-])|[[:punct:]]", "\\1", as.matrix(z))
     X..1. X..2.  
[1,] "1"   "6"    
[2,] "2"   "7.235"
[3,] "3"   "8"    
[4,] "4"   "9"    
[5,] "5"   "-10"  

Here I am keeping the . and -.

And I guess , the next step is to coerce you result to a numeric matrix, SO here I combine the 2 steps like this:

matrix(as.numeric(sub("([.-])|[[:punct:]]", "\\1", as.matrix(z))),ncol=2)
   [,1]    [,2]
[1,]    1   6.000
[2,]    2   7.235
[3,]    3   8.000
[4,]    4   9.000
[5,]    5 -10.000