AWK: How can I print averages of consecutive numbers in a file, but skip over alphabetical characters/strings? - awk

Question

I've figured out how to get the average of a file that contains numbers in all lines such as:
Numbers.txt
1
2
4
8
Output:
Average: 3.75
This is the code I use for that:
awk '{ sum += $1; tot++ } END { print sum / tot; }' Numbers.txt
However, the problem is that this doesn't take into account possible strings that might be in the file. For example, a file that looks like this:
NumbersAndExtras.txt
1
2
4
8
Hello
4
5
6
Cat
Dog
2
4
3
For such a file I'd want to print the multiple averages of the consecutive numbers, ignoring the strings such that the result looks something like this:
Output:
Average: 3.75
Average: 5
Average: 3
I could devise some complicated code that might accomplish that with variables and 'if' statements and loops and whatnot, but I've been told it's easier than that given some of awk features. I'd like to know how that might look like, along with an explanation of why it works.

Answer 1

BEGIN runs before reading the first line from file. Set sum and count to 0.
awk 'BEGIN{ sum=0; count=0} {if ( /[a-z][A-Z]/ ) { if (count > 0) {avg = sum/count; print avg;} count=0; sum=0} else { count++; sum += $1} } END{if (count > 0) {avg = sum/count; print avg}} ' NumbersAndExtras.txt
When there is an alphabet on the line, calculate and print average so far.
And do the same in the END block that runs after processing the whole file.

Answer 2

Keep it simple:
awk '/^$/{next}
/^[0-9]+/{a+=$1+0;c++;next}
c&&a{print "Average: "a/c;a=c=0}
END{if(c&&a){print "Average: "a/c}}' input_file
Results:
Average: 3.75
Average: 5
Average: 3

Answer 3

Another one:
$ awk '
function avg(s, c) { print "Average: ", s/c }
NF && !/^[[:digit:]]/ { if (count) avg(sum, count); sum = 0; count = 0; next}
NF { sum += $1; count++ }
END {if (count) avg(sum, count)}
' <file

Answer 4

Note: The value of this answer in explaining the solution; other answers offer more concise alternatives.
Try the following:
Note that this is an awk command with a script specified as a multi-line shell string literal - you can paste the whole thing into your terminal to try it; while it is possible to cram this into a single line, it hurts readability and the ability to comment:
awk '
# Define output function that prints an average.
function printAvg() { print "Average: ", sum/count }
# Skip blank lines
NF == 0 { next}
# Is the line non-numeric?
/[[:alpha:]]/ {
# If this line ends a numeric block, print its
# average now and reset the variables to start the next group.
if (count) {
printAvg()
wasNum = sum = count = 0
}
# Skip to next line.
next
}
# Numeric line: set flag, sum, and increment counter.
{ sum += $1; count++ }
# Finally:
END {
# If there is a group whose average has not been printed yet,
# do it now.
if (count) printAvg()
}
' NumbersAndExtras.txt
If we condense whitespace and strip the comments, we still get a reasonably readable solution, as long as we still use multiple lines:
awk '
function printAvg() { print "Average: ", sum/count }
NF == 0 { next}
/[[:alpha:]]/ { if (count) { printAvg(); sum = count = 0 } next }
{ sum += $1; count++ }
END { if (count) printAvg() }
' NumbersAndExtras.txt