[SOLVED] awk syntax for calculating average and standard deviation

ProgrammingThis forum is for all programming questions.
The question does not have to be directly related to Linux and any language is fair game.

Notices

Welcome to LinuxQuestions.org, a friendly and active Linux Community.

You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!

Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.

awk syntax for calculating average and standard deviation

I have a data in a column.

Code:

2
4
7
3
5

I want to calculate average and standard deviation. As first step I want to calculate average for the data than calculate (del=data - avg) for all the data.

I also think it's risky to rely on NR for the calculation, if there's a possibility of blank lines or non-numeric data occurring in the input. It would be safer to test for proper input and keep a running tab of the number of lines processed.

Code:

#! /usr/bin/awk -f
{
if ( $1 ~ /^[[:digit:]]+$/ )
{ sum += num[++n] = $1 }
}
END{
avg=( sum / n )
print "avg = "avg
print "x ( x - avg )"
for ( i=1 ; i<=n ; i++ )
print num[i] , ( num[i] - avg )
}

grail will probably come back and show me how to write it in half the space, of course.

Edit: if there could be decimal or negative numbers, you'll have to widen the test. Something like this:

Code:

if ( $1 ~ /^-?[[:digit:]]+(\.[[:digit:]]+)?$/ )

Edit2: I just found an easier way to determine if a field is numeric.

Code:

if ( $1 + 0.0 == $1 )

Last edited by David the H.; 04-21-2011 at 03:25 AM.
Reason: as stated

I want to calculate average and standard deviation for each column starting from column 2 until 5 separately.
After that I want to calculate the average and standard deviation line by line starting from column 2 until column 5 from each line.

For achieve this I tried to work out from model data for calculating average and standard deviation. I just wonder how to write awk code for doing this.

LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.