Divide two elements using awk

Question

I want to do the following calculation using awk: (Element2-Element1)/Element1

Element 1 Position: Column x, Row j

Element 2 Position: Column x, Row i

let x=1, j=2, i=6

Input:

0 2 7 2 3 3

desired Output:

0.5

I dont know how to change FNR inside of the AWK script and opening an awk process just to read each Element and then dividing them by using another awk doesnt feel good.

Thanks in advance!

Hi Roman, j will not be greater than i. It will always be the first line of a column. Im trying to figure out how to skip possible zeros in the first line of each column right now. — Tuni
– Tuni, Commented Sep 19, 2017 at 17:41
what do mean skip? If the third line starts with 0 - should it be skipped, should the remaining lines be reordered? — RomanPerekhrest
– RomanPerekhrest, Commented Sep 19, 2017 at 17:45
What formula did you use to get to the resulting output of 0.5. Can you run through your mathematics with us, manually, so that we can translate into awk? — zedfoxus
– zedfoxus, Commented Sep 19, 2017 at 17:55

anubhava · Accepted Answer · 2017-09-19 17:45:06Z

1

You can use this awk command:

awk -v x=1 -v j=2 -v i=6 'NR==j{e1=$x} NR==i{e2=$x} END{if (el) print (e2-e1)/e1}' file 0.5

edited Sep 19, 2017 at 17:45

answered Sep 19, 2017 at 17:26

anubhava

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2 Comments

Tuni Over a year ago

how can i catch the 0 in the beginning of each line? I dont want inf as output. Or is it possible to take the 2nd value in each column, if the 1st is equal to 0?

anubhava Over a year ago

In that case use { if (e1) print (e2-e1)/e1 } in END block.

RomanPerekhrest · Accepted Answer · 2017-09-19 17:43:14Z

1

j will not be greater than i.

awk solution:

awk 'BEGIN{ x=1; j=2; i=6 }NR==j{ el1=$x }NR==i{ print ($x-el1)/el1; exit }' file 0.5

edited Sep 19, 2017 at 17:43

answered Sep 19, 2017 at 17:27

RomanPerekhrest

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2 Comments

RomanPerekhrest Over a year ago

@anubhava, that condition was not mentioned in the question, that's your condition

RomanPerekhrest Over a year ago

@anubhava, j will not be greater than i.

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