Display the standard deviation of a column of numbers with awk

awk '{sum+=$1; sumsq+=$1*$1} END {print sqrt(sumsq/NR - (sum/NR)**2)}' file.dat

6
By: kaan
2009-03-24 21:56:40

2 Alternatives + Submit Alt

What Others Think

I was finding that this was 'blowing up' when processing a large number (1000's) of lat/long positions with an error message about attempting to SQRT a negative number. Apparently the correct way is to do two passes, compute the mean first, sum the difference between value & mean. You can do this with: awk '{sum+=$1; array[NR]=$1} END {for(x=1;x<=NR;x++){sumsq+=((array[x]-(sum/NR))**2);}print sqrt(sumsq/NR)}' file.dat
mungewell · 473 weeks ago
can you help me how to edit this command, if I have the values in 2nd column?
siti · 433 weeks and 1 day ago
siti: Just replace all occurrences of $1 with $2 (in either version). Thanks to mungewell for pointing out the overflow problem, and to ashawley for the elegant code.
kaan · 433 weeks ago
Can someone help me to modify this code to be able to normalize each value of the column. I guess, after having the mean and the standard deviation, this should be pretty easy. thanks in advance.
anurag_bagaria · 398 weeks ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

You must be signed in to comment.

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands



Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: