consecutive row comparison in awk (?) - Shell Programming and Scripting

ogga · #1 07-23-2008

hi, I'm totally new to this forum and to awk.

I have what I thought was a simple problem, but I can't get anything to work. Here is an example input file:

3.85 4018.4
3.9 4068.4
3.95 4082.9
4 4099.7

# Property:.......etc.
0 4733.3
0.05 4659.7
0.1 4585.6
0.15 4466.2

Two fields separated at arbitrary positions by blank lines and label headers.

I want to compare the differences between $2 for all consecutive rows but only within each block delimited by the header: i.e.
ABS(4733.3 - 4659.7),
ABS(4659.7 - 4585.6),
but not:
ABS(4099.7 - 4733.3), etc.

I want to record the largest difference (and the location!).

Thanks for any help,
Oscar

Annihilannic · #2 07-23-2008

Something like this?

Code:

awk '
        /^$/ { next }
        /^#/ { print maxdiffrec, maxdiff; print; prev=""; maxdiff=0; next }
        prev != "" {
                absdiff=prev>$2 ? prev-$2 : $2-prev
                if (absdiff > maxdiff) { maxdiff=absdiff; maxdiffrec=NR }
        }
        { prev=$2 }
        END { print maxdiffrec, maxdiff }
'

ogga · #3 07-24-2008

dude! you're my saviour!

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