[SOLVED] awk syntax for calculating average and standard deviation

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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 04:25 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.

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