Arithmetic operation between columns using loop variable

Shell Programming and Scripting
1

Hi
I have a file with 3 columns. say,
infile:

1  50   68
34 3   23
23  4  56
-------
-------

I want to generate n files from this file using a loop so that 1st column in output file is (column1 of infile/(2*n+2.561))

I am doing like this:

for ((i=1; i<=3; i++))
do
  a=`echo "2*$i+2.561" | bc -l`   
  awk '{ printf"%.8f %.8f %.8f\n", ($1/a), $2, $3 }' infile >> out$i
done

but it seems variable a has to be defined within awk. how can I use i in it? Please help

2

like this?

awk '{r=$1/(2*NR)+2.561; print r,$2,$3}' infile

output:

3.061 50 68
11.061 3 23
6.39433 4 56
3

To declare a variable within awk use -v option..so the above awk could be as

awk -v var="$a" '{ printf"%.8f %.8f %.8f\n", $1/var, $2, $3 }' infile >> out$i
4

thanks