Awk Calc Avg Rows Below Certain Line - bash

Question

I'm having trouble calculating an average of specific numbers in column BELOW a specific text identifier using awk. I have two columns of data and I'm trying to start the average keying on a common identifier that repeats, which is 01/1991. So, awk should calc the average of all lines beginning with 01/1991, which repeats, using the next 21 lines with total count of rows for average = 22 for the total number of years 1991-2012. The desired output is an average of each TextID/Name entry for all the January's (01) for each year 1991 - 2012 show below:
TextID/Name 1
Avg: 50.34
TextID/Name 2
Avg: 45.67
TextID/Name 3
Avg: 39.97
...
sample data:
TextID/Name 1
01/1991, 57.67
01/1992, 56.43
01/1993, 49.41
..
01/2012, 39.88
TextID/Name 2
01/1991, 45.66
01/1992, 34.77
01/1993, 56.21
..
01/2012, 42.11
TextID/Name 3
01/1991, 32.22
01/1992, 23.71
01/1993, 29.55
..
01/2012, 35.10
continues with the same data for TextID/Name 4
I'm getting an answer using this code shown below but the average is starting to calculate BEFORE the specific identifier line and not on and below that line (01/1991).
awk '$1="01/1991" {sum+=$2} (NR%22==0){avg=sum/22;print"Average: "avg;sum=0;next}' myfile
Thanks and explanations of the solution is greatly appreciated! I have edited the original answer with more description - thank you again.

Answer 1

If you look at your file, the first field is "01/1991," with a comma at the end, not "01/1991". Also, NR%22==0 will look at line numbers divisible by 22, not 22 lines after the point it thinks you care about.
You can do something like this instead:
awk '
BEGIN { l=-1; }
$1 == "01/1991," {
l=22;
s=0;
}
l > 0 { s+=$2; l--; }
l == 0 { print s/22; l--; }'
It has a counter l that it sets to the number of lines to count, then it sums up that number of lines.
You may want to consider simply summing all lines from one 01/1991 to the next though, which might be more robust.

Answer 2

If you're allowed to use Perl instead of Awk, you could do:
#!/usr/bin/env perl
$start = 0;
$have_started = 0;
$count = 0;
$sum = 0;
while (<>) {
$line = $_;
# Grab the value after the date and comma
if ($line = /\d+\/\d+,\s+([\d\.]+)/) {
$val = $+;
}
# Start summing values after 01/1991
if (/01\/1991,\s+([\d\.]+)/) {
$have_started = 1;
$val = $+;
}
# If we have started counting,
if ($have_started) {
$count++;
$sum += $+;
}
}
print "Average of all values = " . $sum/$count;
Run it like so:
$ cat your-text-file.txt | above-perl-script.pl