How do I calculate the mean of a column

Question

Anyone know how can I calculate the mean of one these columns (on linux)??

sda               2.91    20.44    6.13    2.95   217.53   186.67    44.55     0.         


        

Answer 1

Awk:

awk '{ total += $2 } END { print total/NR }' yourFile.whatever

Read as:

• For each line, add column 2 to a variable 'total'.
• At the end of the file, print 'total' divided by the number of records.

Answer 2

Perl solution:

perl -lane '$total += $F[1]; END{print $total/$.}' file

-a autosplits the line into the @F array, which is indexed starting at 0
$. is the line number

If your fields are separated by commas instead of whitespace:

perl -F, -lane '$total += $F[1]; END{print $total/$.}' file

To print mean values of all columns, assign totals to array @t:

perl -lane 'for $c (0..$#F){$t[$c] += $F[$c]}; END{for $c (0..$#t){print $t[$c]/$.}}' 

output:

0
0.485
14.38
1.74
0.888333333333333
77.27
49.8266666666667
39.91
1.29833333333333
434.131666666667

Answer 3

David Zaslavsky for the fun of it:

with open("mean.txt", 'r') as f: 
    n,t = map(sum, zip(*((1, float(line.split()[1])) for line in f)))
print t/n

Answer 4

You can use python for that, is available in Linux.

If that comes from a file, take a look at this question, just use float instead.

For instance:

#mean.py 
def main():
    with open("mean.txt", 'r') as f:
        data = [map(float, line.split()) for line in f]

    columnTwo = []
    for row in data:
        columnTwo.append( row[1] )

    print  sum(columnTwo,0.0) / len( columnTwo )



if __name__=="__main__":
    main()

Prints 14.38

_{I just include the data in the mean.txt file, not the row header: "sda"}

Answer 5

Simple-r will calculate the mean with the following line:

r -k2 mean file.txt

for the second column. It can also do much more sophisticated statistical analysis, since it uses R environment for all of its statistical analysis.