CODEWITHSUNDEEP
bashmathawk
Joana Carvalho
Joana Carvalho

Reputation: 99

How to do math operations in a single column in bash and/or using awk?

I have a column of several rows like this:

20.000
15.000
42.500
42.500
45.000
45.000
50.000
50.000
50.000
50.000
50.000
50.000
50.000
50.000
50.000

and I need to end up with a file where:

first element is 20/2

second element is the previous value + 15/2

third element is the previous values + 42.5/2

an so on until the end

My problem is how to do the "loop".

Upvotes: 2

Views: 2340

Answers (5)

karakfa
karakfa

Reputation: 67497

simply,

$ awk '{print v+=$1/2}' file

10
17.5
38.75
60
82.5
105
130
155
180
205
230
255
280
305
330

you can set printf formatting if needed

Upvotes: 2

Mohit Rathore
Mohit Rathore

Reputation: 428

I think you might looking for for loop

awk '{for (i = 1; i <= NF; i++) print  temp = temp + $i/2  }' filename

remember one thing, i refers to a column number if you want to run this operation in only one column you can change value of

i = column number; i <= column number;

You can use this loop for complex scenario.

If you want to change the separator you can use parameter like -F and the separator.

awk -F ":" '{}' filename

enter image description here

Upvotes: 0

shirish
shirish

Reputation: 678

Try this:

awk '{prev += ($0) / 2; printf("%.3f\n", prev);}' a2.txt


Input:

20.000
15.000
42.500
42.500
45.000
45.000
50.000
50.000
50.000
50.000
50.000
50.000
50.000
50.000
50.000


Output:

10.000
17.500
38.750
60.000
82.500
105.000
130.000
155.000
180.000
205.000
230.000
255.000
280.000
305.000
330.000


Upvotes: 1

Tyl
Tyl

Reputation: 5252

I guess you need output to be one line:

awk '{s+=$1/2; out = out s " ";} END{print out}' file
#=> 10 17.5 38.75 60 82.5 105 130 155 180 205 230 255 280 305 330

There's an extra space at the end which I think has no harm.
You can remove it if you don't want it.

Upvotes: 0

choroba
choroba

Reputation: 241868

Perl to the rescue:

perl -lne 'print $s += $_ / 2' input-file > output-file
  • -l removes newlines from input and adds them to output
  • -n reads the input line by line, executing the code for each
  • $_ is the value read from each line
  • / 2 is division by 2
  • += is the operator that adds its ride hand side to its left hand side and stores the result in the left hand side, returning the new value. I named the variable $s as in "sum".

Upvotes: 3

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