How to divide a list of values by a number in command line?

Question

I am trying to translate a simple program to the command line using unix utilities. For example, if I have a frequency list (after piping through uniq and sort)

5 x
4 y
1 z

I want to print out, instead of the frequencies, the fraction of the times they occur:

0.5 x
0.4 y
0.1 z

(I have a python program that does this, but I wanted to know if this could be done through the command line itself.)

So far, I have tried to compute the sum

<...>| awk -F" " '{print $1}' | tr '\n' +; echo 0 | bc

but this is just giving me the output 5+1+4+0 without computing it.

EDIT: I got the sum . I modified the above command to

<...>| awk -F" " '{print $1}' | echo $(tr '\n' +; echo 0) | bc > sum 

and the correct result is stored in sum. Now I just want to divide the original list by sum and display it.

Answer 1

awk '{ f[$2] = $1; SUM += $1} END { for (i in f) { print f[i]/SUM, i } }' </tmp/data

Answer 2

You can do the summing in awk, and the dividing as well. This will be simpler than invoking bc since you have other data on each line.

This prints the sum of the first field of the input lines:

awk '{sum += $1} END {print $1}'

So you can save the input data, compute the sum, and continue processing the data.

data=$(…)
sum=$(printf '%s\n' "$data" | awk '{sum += $1} END {print $1}')
printf '%s\n' "$data" | awk -v sum="$sum" '{ $1 /= sum; print }'

Or you might make a single pass in awk, retaining all the data in memory.