Select current and previous line if certain value is found - awk

Question

To figure out my problem, I subtract column 3 and create a new column 5 with new values, then I print the previous and current line if the value found is equal to 25 in column 5.
Input file
1 1 35 1
2 5 50 1
2 6 75 1
4 7 85 1
5 8 100 1
6 9 125 1
4 1 200 1
I tried
awk '{$5 = $3 - prev3; prev3 = $3; print $0}' file
output
1 1 35 1 35
2 5 50 1 15
2 6 75 1 25
4 7 85 1 10
5 8 100 1 15
6 9 125 1 25
4 1 200 1 75
Desired Output
2 5 50 1 15
2 6 75 1 25
5 8 100 1 15
6 9 125 1 25
Thanks in advance

Answer 1

you're almost there, in addition to previous $3, keep the previous $0 and only print when condition is satisfied.
$ awk '{$5=$3-p3} $5==25{print p0; print} {p0=$0;p3=$3}' file
2 5 50 1 15
2 6 75 1 25
5 8 100 1 15
6 9 125 1 25
this can be further golfed to
$ awk '25==($5=$3-p3){print p0; print} {p0=$0;p3=$3}' file
check the newly computed field $5 whether equal to 25. If so print the previous line and current line. Save the previous line and previous $3 for the computations in the next line.

Answer 2

You are close to the answer, just pipe it another awk and print it
awk '{$5 = $3 - prev3; prev3 = $3; print $0}' oxxo.txt | awk ' { curr=$0; if($5==25) { print prev;print curr } prev=curr } '
with Inputs:
$ cat oxxo.txt
1 1 35 1
2 5 50 1
2 6 75 1
4 7 85 1
5 8 100 1
6 9 125 1
4 1 200 1
$ awk '{$5 = $3 - prev3; prev3 = $3; print $0}' oxxo.txt | awk ' { curr=$0; if($5==25) { print prev;print curr } prev=curr } '
2 5 50 1 15
2 6 75 1 25
5 8 100 1 15
6 9 125 1 25
$

Answer 3

Could you please try following.
awk '$3-prev==25{print line ORS $0,$3} {$(NF+1)=$3-prev;prev=$3;line=$0}' Input_file | column -t

Answer 4

Here's one:
$ awk '{$5=$3-q;t=p;p=$0;q=$3;$0=t ORS $0}$10==25' file
2 5 50 1 15
2 6 75 1 25
5 8 100 1 15
6 9 125 1 25
Explained:
$ awk '{
$5=$3-q # subtract
t=p # previous to temp
p=$0 # store previous for next round
q=$3 # store subtract value for next round
$0=t ORS $0 # prepare record for output
}
$10==25 # output if equals
' file
No checking for duplicates so you might get same record printed twice. Easiest way to fix is to pipe the output to uniq.