Extract multiple recurring text patterns

Question

I have a string looking like this:

txt <- "|M  CHG  6  44  -1  48  -1  53  -1  63   1  64   1  65   1|"

The first digit (6) means that the pattern \\s+\\d+\\s+[\\+-]?\\d+ recurs 6 times. Actually I'm only interested in the second (potentially signed) digit of this pattern. So I'm looking for a function or regular expression which gives me as a result

[1] "-1" "-1" "-1" "1" "1" "1"

I tried it with

gsub( "^\\|M\\s+CHG\\s+\\d+(\\s+\\d+\\s+([\\+-]?\\d+))+\\|$", replacement="\\2", x=txt, perl=TRUE )

as well as

str_replace_all( x, perl( "^\\|M\\s+CHG\\s+\\d+(\\s+\\d+\\s+([\\+-]?\\d+))+\\|$" ), "\\2" )

but in both cases I got only the last occurrence returned.

Answer 1

One solution would be to strip the beginning characters (I've done this with a regex but you might want to use substr or simillar. Then matrix into the required dimensions and return the column you want:

#  regex to strip superfluous characters
#  but `substring( txt , 10 )` would work just as well in this example
pat <- "^\\|M\\s+CHG\\s+\\d+\\s+(.*)\\|$"
x <- gsub( pat , "\\1" , txt )

#  Get result
matrix( unlist( strsplit( x , "\\s+" ) ) , ncol = 2 , byrow = 2 )[,2]
# [1] "-1" "-1" "-1" "1"  "1"  "1"

The intermediate matrix looks like this:

#     [,1] [,2]
#[1,] "44" "-1"
#[2,] "48" "-1"
#[3,] "53" "-1"
#[4,] "63" "1" 
#[5,] "64" "1" 
#[6,] "65" "1" 

Answer 2

I'd just use a split on with the end | removed. I'd only take what's after the 3rd element and the odd ones.

    var txt, txtArray, result;

txt = "|M  CHG  6  44  -1  48  -1  53  -1  63   1  64   1  65   1|";

// Remove the end '|';
txt = txt.slice(0, -1);

// Split on one or more space...
txtArray = txt.split(/\s+/);


// Grab the odd ones only after the third element...
result = txtArray.filter(function(n, i){
  return i > 3 && i % 2 === 0;
});

console.log( result );

Answer 3

Another one

txt <- "|M  CHG  6  44  -1  48  -1  53  -1  63   1  64   1  65   1|"    


#original
#txtsplit<-unlist(strsplit(txt, "\\s+"))
#n=as.numeric(txtsplit[3])
#o<-txtsplit[4+seq(from=1, by=2, length.out=n)]

#fixed
txtsplit<-unlist(strsplit(txt, "\\||\\s+"))
n=as.numeric(txtsplit[4])
o<-txtsplit[5+seq(from=1, by=2, length.out=n)]

#>o
[1] "-1" "-1" "-1" "1"  "1"  "1"