Is there a way to get the min, max, median, and average of a list of numbers in a single command?

Question

I have a list of numbers in a file, one per line. How can I get the minimum, maximum, median and average values? I want to use the results in a bash script.

Although my immediate situation is for integers, a solution for floating-point numbers would be useful down the line, but a simple integer method is fine...

Answer 1

You can use the R programming language:

$ DATA="6 2 4 3 1"
$ R --slave << EOF
d <- scan()
$DATA

summary(d)
EOF

The empty line after $DATA is necessary for scan() to recognize end of input.

Output:

Read 5 items
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
    1.0     2.0     3.0     3.2     4.0     6.0 

Also works for floating points:

$ DATA="6.1 2.2 4.3 3.4 1.5"

Output:

Read 5 items
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
    1.5     2.2     3.4     3.5     4.3     6.1 

Alternatively:

$ R --slave << EOF
d <- scan()
$DATA

min(d)
max(d)
mean(d)
median(d)
EOF

Output:

Read 5 items
[1] 1.5
[1] 6.1
[1] 3.5
[1] 3.4

I am certain that it is possible to format the output to be nicer, but I am far from an R expert. You will have to look that up yourself.

Answer 2

Min, max and average are pretty easy to get with awk:

% echo -e '6\n2\n4\n3\n1' | awk 'NR == 1 { max=$1; min=$1; sum=0 }
   { if ($1>max) max=$1; if ($1<min) min=$1; sum+=$1;}
   END {printf "Min: %d\tMax: %d\tAverage: %f\n", min, max, sum/NR}'
Min: 1  Max: 6  Average: 3,200000

Calculating median is a bit more tricky, since you need to sort numbers and store them all in memory for a while or read them twice (first time to count them, second - to get median value). Here is example which stores all numbers in memory:

% echo -e '6\n2\n4\n3\n1' | sort -n | awk '{arr[NR]=$1}
   END { if (NR%2==1) print arr[(NR+1)/2]; else print (arr[NR/2]+arr[NR/2+1])/2}' 
3

Answer 3

I actually keep a little awk program around to give the sum, data count, minimum datum, maximum datum, mean and median of a single column of numeric data:

#!/bin/sh
sort -n |
awk 'BEGIN{c=0;sum=0;}\
/^[^#]/{a[c++]=$1;sum+=$1;}\
END{ave=sum/c;\
if((c%2)==1){median=a[int(c/2)];}\
else{median=(a[c/2]+a[c/2-1])/2;}\
print sum,"\t",c,"\t",ave,"\t",median,"\t",a[0],"\t",a[c-1]}'

The above script reads from stdin, and prints tab-separated columns of output on a single line.

Answer 4

I'll second lesmana's choice of R and offer my first R program. It reads one number per line on standard input and writes four numbers (min, max, average, median) separated by spaces to standard output.

#!/usr/bin/env Rscript
a <- scan(file("stdin"), c(0), quiet=TRUE);
cat(min(a), max(a), mean(a), median(a), "\n");

Answer 5

Just for the sake of having a variety of options presented on this page, Here are two more ways:

1: octave

• GNU Octave is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments.

Here is a quick octave example.

octave -q --eval 'A=1:10;
  printf ("# %f\t%f\t%f\t%f\n", min(A), max(A), median(A), mean(A));'  
# 1.000000        10.000000       5.500000        5.500000

---

2: bash + single-purpose tools.

For bash to handle floating-point numbers, this script uses numprocess and numaverage from package num-utils.

PS. I've also had a reasonable look at bc, but for this particular job, it doesn't offer anything beyond what awk does. It is (as the 'c' in 'bc' states) a calculator—a calculator which requires a much programming as awk and this bash script...

---

arr=($(sort -n "LIST" |tee >(numaverage 2>/dev/null >stats.avg) ))
cnt=${#arr[@]}; ((cnt==0)) && { echo -e "0\t0\t0\t0\t0"; exit; }
mid=$((cnt/2)); 
if [[ ${cnt#${cnt%?}} == [02468] ]] 
   then med=$( echo -n "${arr[mid-1]}" |numprocess /+${arr[mid]},%2/ )
   else med=${arr[mid]}; 
fi     #  count   min       max           median        average
echo -ne "$cnt\t${arr[0]}\t${arr[cnt-1]}\t$med\t"; cat stats.avg 

Answer 6

If you're more interested in utility rather than being cool or clever, then perl is an easier choice than awk. By and large it will be on every *nix with consistent behaviour, and is easy and free to install on windows. I think it's also less cryptic than awk, and there will be some stats modules you could use if you wanted a halfway house between writing it yourself and something like R. My fairly untested (in fact I know it has bugs but it works for my purposes) perl script took about a minute to write, and I'd guess the only cryptic part would be the while(<>), which is the very useful shorthand, meaning take the file(s) passed as command line arguments, read a line at a time and put that line in the special variable $_. So you could put this in a file called count.pl and run it as perl count.pl myfile. Apart from that it should be painfully obvious what's going on.

$max = 0;
while (<>) {
 $sum = $sum + $_;
 $max = $_ if ($_ > $max);
 $count++;
}
$avg=$sum/$count;
print "$count numbers total=$sum max=$max mean=$avg\n";