I would like to insert new lines in text files if there are missing values.
I have for example the following text file (A.txt), for which line 5 is missing. In addition, as the file should have 12 lines the lines 11-12 are also missing. 

```
1 2.30
2 3.01
3 3.22
4 3.34
6 3.01
7 2.90
8 2.99
9 3.00
10 3.02

```

My expected output is the following. For missing cases a line should be added with the number and NA. As you see, this happened as desired at line 5, 11 and 12:

```
1 2.30
2 3.01
3 3.22
4 3.34
5 NA
6 3.01
7 2.90
8 2.99
9 3.00
10 3.02
11 NA
12 NA

```

I am able to do this by using the following script:

```
f1=/my-directory/
echo "new file" > "$f1"/newfile.txt  

for i in {1..12}; do
l=$(awk '{print $1}' /"$f1"/A.txt | grep -wE ^$i /"$f1"/A.txt)
if grep --quiet -wE ^$i /"$f1"/A.txt; then echo "$l" >> "$f1"/newfile.txt; else echo "$i NA" >> "$f1"/newfile.txt; fi

done

```

This works fine. The problem is however that I need to do this for about 600 files containing more than about 160000 lines. The loop solution would therefore take too much time searching through all lines. My question is: is there a simpler solution that could do this?