I have files containing data set which contain 11,000 rows. I have to run a loop through each row, this is taking me 25minutes for each file. I am using following code:

     z <- read.zoo("Title.txt", tz = "")
  for(i in seq_along(z[,1])) {
    if(is.na(coredata(z[i,1]))) next
   ctr <- i
    while(ctr < length(z[,1])) {
     if(       (   abs  ( coredata(z[i,1]) -coredata(z[ctr+1,1])  )      )  > std_d) {
       z[ctr+1,1] <- NA
       ctr <- ctr + 1
  
      } else {
  break
    }
 }
}

Where Title. txt is file containing 11,000rows. It looks like (first five rows):

"timestamp" "mesured_distance" "IFC_Code" "from_sensor_to_river_bottom"
 "1" "2012-06-03 12:30:07-05" 3188 1005 3500
 "2" "2012-06-03 12:15:16-05" 3189 1005 3500
 "3" "2012-06-03 12:00:08-05" 3185 1005 3500
 "4" "2012-06-03 11:45:11-05" 3191 1005 3500
 "5" "2012-06-03 11:30:15-05" 3188 1005 3500

I wish to receive help on how should I increase the speed for this code? Thank you for your consideration.

I have files containing data sets which contain 11,000 rows. I have to run a loop through each row, which is taking me 25 minutes for each file.

     z <- read.zoo("Title.txt", tz = "")
  for(i in seq_along(z[,1])) {
    if(is.na(coredata(z[i,1]))) next
   ctr <- i
    while(ctr < length(z[,1])) {
     if(       (   abs  ( coredata(z[i,1]) -coredata(z[ctr+1,1])  )      )  > std_d) {
       z[ctr+1,1] <- NA
       ctr <- ctr + 1
  
      } else {
  break
    }
 }
}

Where Title.txt is a file containing 11,000 rows. It looks like this (first five rows):

"timestamp" "mesured_distance" "IFC_Code" "from_sensor_to_river_bottom"
 "1" "2012-06-03 12:30:07-05" 3188 1005 3500
 "2" "2012-06-03 12:15:16-05" 3189 1005 3500
 "3" "2012-06-03 12:00:08-05" 3185 1005 3500
 "4" "2012-06-03 11:45:11-05" 3191 1005 3500
 "5" "2012-06-03 11:30:15-05" 3188 1005 3500

How can I increase the speed of this code?