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Dividing a column by it's first number

 
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# 1  
Old 06-25-2011
Dividing a column by it's first number
Hi!

Is there an easy way (maybe using awk??) to divide the values of one column of the file by it's first entry..

If I have a column:

3
4
5
6
7

I would like to divide it by 3.

I want to do this for more than 100 files, so it wouldn't be practical to open file by file and manually write the first number in the column for the calculation Smilie
# 2  
Old 06-25-2011
Is it the only column in those files? If not, then post sample input and desired output, please.
# 3  
Old 06-25-2011
try this:
Code:
awk 'BEGIN{first_line=0;divide_by=1;}{if(first_line==0){first_line=1; divide_by=$1;}print $1/divide_by;}END{}' your_file

it doesn't care about the number of column the file has, it considers only the first column
Last edited by Scott; 06-25-2011 at 11:23 AM.. Reason: Code tags
This User Gave Thanks to ggmas For This Post:
cosmologist
# 4  
Old 06-25-2011
The file is really big, but this is a sample of the first few lines:
Code:
5200.  1.212681E-13
5205.40000000001  1.222450E-13
5210.8  1.227840E-13
5216.20000000001  1.238888E-13
5221.60000000001  1.254731E-13
5227.00000000001  1.260795E-13
5232.40000000001  1.232285E-13
5237.80000000001  1.223140E-13
5243.20000000001  1.253938E-13
5248.60000000001  1.263059E-13
5254.00000000001  1.242172E-13
5259.40000000001  1.224269E-13
5264.80000000001  1.207516E-13
5270.20000000001  1.192588E-13
5275.60000000001  1.194812E-13
5281.00000000001  1.213403E-13
5286.40000000001  1.237752E-13
5291.80000000001  1.245416E-13
5297.20000000001  1.245865E-13
5302.6  1.251646E-13
5308.00000000001  1.254696E-13
5313.40000000001  1.249386E-13
5318.80000000001  1.252902E-13
5324.20000000001  1.243008E-13
5329.6  1.224932E-13
5335.00000000001  1.228107E-13
5340.40000000001  1.217807E-13
5345.80000000001  1.205050E-13
5351.20000000001  1.213104E-13
5356.60000000001  1.228911E-13
5362.  1.238935E-13
5367.40000000001  1.224568E-13
5372.8  1.207849E-13
5378.20000000001  1.212063E-13
5383.60000000001  1.219594E-13
5389.00000000001  1.222528E-13

I would like to divide the second column by its first number ( 1.212681E-13 in this case).
# 5  
Old 06-25-2011
Code:
awk 'BEGIN{first_line=0;divide_by=1;}{if(first_line==0){first_line=1; divide_by=$2;}print $2/divide_by;}END{}' your_file

The column is indicated by the value after $, in this case $2 means that awk takes the column 2
Moderator's Comments:
Mod Comment
Please use code tags when posting data and code samples!
Last edited by vgersh99; 06-25-2011 at 08:41 AM.. Reason: code tags, please!
# 6  
Old 06-25-2011
another awk solution:
Code:
~/unix.com$ awk 'BEGIN{getline;x=$2;print}{$2=$2/x}1' input_file > output_file

# 7  
Old 06-25-2011
Is there a way to get it divide the column by the first non-zero value in that column? Smilie ... some columns have the first 50+ entries = 0 ... I wonder if the first non zero value in the column can be found and divide the whole column by it?

Thanks!
Last edited by cosmologist; 06-25-2011 at 03:41 PM..
 
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