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So I have file with 3 columns:

9 1 2
2 2 1
5 3 1
7 3 1
5 3 1
2 3 1
8   2 1
3 2 1
1 1 1

I want to remove from the first column particular values and the relative rows, for example 2 and 5 (that are present more times in the same column) and decrement all the values in the first column that are greater than that value. So if I remove first the number 2 I want to obtain:

8 1 2

4 3 1
6 3 1
4 3 1

7 2 1
2 2 1
1 1 1

and then 5(that now is 4) my output would be:

7 1 2


5 3 1


6 2 1
2 2 1
1 1 1

How can I do that? Consider that I have to remove lot of values in the real case and the file is really big.

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  • I'm not sure I understand what you mean. How do you decide which rows to remove and why? Can you expand your explanation a little more? Commented May 7, 2018 at 19:05
  • So the file with the 3 columns is a sparse matrix and the first column are coordinates. I have to remove around 60 values that correspond to particular coordinates of the first column but I want also to remove the corresponding rows and keep the remaining coordinates. If the remaining coordinates are greater than the value (2 as the example) I want to reduce that coordinates value of the first column of 1. Commented May 7, 2018 at 19:17
  • @shiva, is it mandatory to retain empty lines? Commented May 7, 2018 at 19:18
  • No I don't want empty lines. I add them only for clarity of the example. Commented May 7, 2018 at 19:20
  • 1
    How are the lines chosen as to which are deleted? Commented May 7, 2018 at 19:36

1 Answer 1

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bash + awk solution:

i=0;
for n in 2 5; do
    awk -v n="$n" -v iter=$((++i)) \
   'iter == 1{ 
        if ($1 > n) { $1-- } else if ($1 == n) { next }
    }
    iter > 1{
        if ($1 + 1 == n){ next } else if ($1 >= n) $1-- 
    }1' inp_file > tmp_inpfile && mv tmp_inpfile inp_file
done

The final inp_file contents:

7 1 2
5 3 1
6 2 1
2 2 1
1 1 1
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  • can you please explain the code? Thank you. Commented May 8, 2018 at 6:57
  • I recommend you to test this approach on different values in different order. And if it fails in some critical cases - I would rather delete this answer. Commented May 8, 2018 at 7:11

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