add a new column of numbers to whitespace delimited data based on another column of numbers using Bash utilities

Question

I want to perform a simple calculation on each number in a column of whitespace delimited data using Bash utilities such as cut and bc. The data may look like something such as the following:

string 0.998663 string string string
string 0.998592 string string string
string 0.999096 string string string

Let's say I want to change the show the numbers in the second column to three significant figures. I want to add another column of these new numbers to this data directly following the second column. So, the result may look like something such as the following:

string 0.998663 0.999 string string string
string 0.998592 0.999 string string string
string 0.999096 0.999 string string string

I know that I can manually cycle through all of this data and then construct new columns of data, but I imagine that there is a more efficient way of doing this. Would you happen to know of some clever way of doing this?

score 4 · Accepted Answer · answered Feb 25 '13 at 11:49

4

try this short line:

awk '$2=$2" "sprintf("%.3f",$2)' file

with your example data:

kent$  echo "string 0.998663 string string string
string 0.998592 string string string
string 0.999096 string string string"|awk '$2=$2" "sprintf("%.3f",$2)'
string 0.998663 0.999 string string string
string 0.998592 0.999 string string string
string 0.999096 0.999 string string string

answered Feb 25 '13 at 11:49

Kent

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+1 but I would use `FS` instead of " " i.e. `awk '$2=$2 FS sprintf("%.3f",$2)' file` – dogbane Feb 25 '13 at 11:58
I knew it could be optimized. Nice solution! – fedorqui Feb 25 '13 at 12:10
This is efficient and simple. Thanks! – d3pd Feb 25 '13 at 14:30

fedorqui · Answer 2 · 2016-06-20T11:33:28.353

1

You can try with:

awk '{printf("%s %s %.3f %s %s %s\n",$1,$2,$2,$3,$4,$5)}' file

Test

$ awk '{printf("%s %s %.3f %s %s %s\n",$1,$2,$2,$3,$4,$5)}' file
string 0.998663 0.999 string string string
string 0.998592 0.999 string string string
string 0.999096 0.999 string string string

edited Jun 20 '16 at 11:33

answered Feb 25 '13 at 11:42

fedorqui

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You don't need a loop here! `awk '{printf("%s %s %.3f %s %s %s\n",$1,$2,$2,$3,$4,$5)}' file` is enough. – dogbane Feb 25 '13 at 11:43
i am not sure if it is fast solution.. you started/stopped awk process linenumber times. – Kent Feb 25 '13 at 11:53

add a new column of numbers to whitespace delimited data based on another column of numbers using Bash utilities

2 Answers2