Shell Programming and Scripting

Hello,

I request your kind help in solving this problem...

I have a file with two columns and "n" number of rows. For the first column, it won't be change. For the second column, I want to take the average of the first three rows. Then assign the averaged value to the first three rows. This process will be applied as well to the following 3 rows, after the changed rows. The output file will have two columns, the unchanged column ($1) and the changed column ($2). To illustrate the problem...

Input file:
$1= 1, 2, 3, 4, 5, 6.....n
$2= 2, 4, 6, 8, 10, 12....n

Output file:
$1= no change
$2= 4, 4, 4, 10, 10, 10....n (average of 2,4,6 is 4. average of 8,10,12 is 10)

So far I have an AWK code that doesn't work:
BEGIN {a[NR]=$2}
{
for (i=1;i<=n;i++) {
avg=(a[i]+a[i+1]+a[i+2])/3;
a[i]=avg;
a[i+1]=avg;
a[i+3]=avg;
i=i+4;
};
}
END {
i=1;
while (i<=n) {print $1, a[i]; i+=1;};
}

I'll appreciate a lot your help!

Solracq

You show an example with 2 rows and n columns, do you want the average of 3 rows (= lines) or 3 columns?
It should be easier if you provide the exact format of the input and the desired output.

Here is the script.Try this out
awkscript.awk

Code:

{if( NR == 2 )
{
    i=1;
    n=split($2,arr,",");
    while(i<=n)
    {
        avg=(arr[i] + arr[i+1] + arr[i+2])/3;
        arr[i]=arr[i+1]=arr[i+2]=avg;
        i=i+3;
    }
    ORS="";
    print $1"=";
    ORS=","
    for(i=1;i<=n;i++){
        print arr[i];
    }
};
}

Invoke it as awk -F"=" -f awkscript.awk Inputfile.txt

Using this code, I will try to make it work... thanks anyways!

hi, I require the average of every three rows or lines in a column, $2. And I need to replace the result with the same three values, rows, I calulated the average. In other words...

Input file (the one i'm using, the "......" means a space line):
$1........$2
10......1348480
11......1364490
12......1347840
13......1414400
14.......1364480
15.......1331200

The output shuld be :
$1........$2
10......1353603.3
11......1353603.3
12......1353603.3 ------------->Average of the first three lines of $2
13......1370026.6
14.......1370026.6
15.......1370026.6------------->Average of the following three lines of $2

the calculation ends till the final record according to the input (approx. 200 records)

I think this makes more clear what I need...

thanks again for you nice help!

Solracq

Assuming you don't have the first row ($1........$2) in your file:

Code:

awk '
{s+=$2;a[NR%3]=$1}
!(NR%3){
  for(i=1;i<4;i++) {
    print a[i%3],s/3
  }
  s=0
}' file

Regards

IT WORKS!!

Thank you again!

Carlos