Maximum and Minimum using awk - unix

Question

How would you find the maximum and minimum a,b,c values for the rows that start with MATH from the following file?
TITLE a b c
MATH 12.3 -0.42 5.5
ENGLISH 70.45 3.21 6.63
MATH 3.32 2.43 9.42
MATH 3.91 -1.56 7.22
ENGLISH 89.21 4.66 5.32
It can not be just 1 command line. It has to be a script file using BEGIN function and END.
I get the wrong minimum value and I end up getting a string for max when I run my program. Please help!
Here is my code for the column a:
BEGIN { x=1 }
{
if ($1 == "MATH") {
min=max=$2;
for ( i=0; i<=NF; i++) {
min = (min < $i ? min : $i)
max = (max > $i ? max : $i)
}
}
}
END { print "max a value is ", max, " min a value is ", min }
Thanks!

Answer 1

This code could demonstrate a concept of what you want:
awk '$1!="MATH"{next}1;!i++{min=$2;max=$2;}{for(j=2;j<=NF;++j){min=(min<$j)?min:$j;max=(max>$j)?max:$j}}END{printf "Max value is %.2f. Min value is %.2f.\n", max, min}' file
Output:
MATH 12.3 -0.42 5.5
MATH 3.32 2.43 9.42
MATH 3.91 -1.56 7.22
Max value is 12.30. Min value is -1.56.
Remove 1 to suppress the messages:
awk '$1!="MATH"{next};...
Script version:
#!/usr/bin/awk
$1 != "MATH" {
# Move to next record if not about "MATH".
next
}
!i++ {
# Only does this on first match.
min = $2; max = $2
}
{
for (j = 2; j <= NF; ++j) {
min = (min < $j) ? min : $j
max = (max > $j) ? max : $j
}
}
END {
printf "Max value is %.2f. Min value is %.2f.\n", max, min
}

Answer 2

look at your for loop
it starts from i=0 so the condition should be
i<NF
instead of
i<= NF
try the following line instead of that line .... i hope you get what u are looking for
for(i=0;i<NF;i++){
rest all looks fine to me.... thanks

Answer 3

The i variable in the for loop should at least begin with 2(the 2rd field), not 0, which represent the whole line, and end with NF.
BEGIN { x=1;min=2147483647;max=-2147483648}
{
if ($1 == "MATH") {
for ( i=2; i<=NF; i++) {
min = (min < $i ? min : $i)
max = (max > $i ? max : $i)
}
}
}
END { print "max a value is ", max, " min a value is ", min }
Run with command:(testawk.script for the above awk script filename, test.data for input data filename)
cat test.data | awk -f testawk.script
output:
max a value is 12.30 min a value is -1.56

Answer 4

I don't have a terminal handy on me right now but something along these lines will get the smallest of each line.
cat YOURFILE | grep "^MATH" | cat test | \
while read CMD; do
A=`echo $CMD | awk '{ print $2 }'`
B=`echo $CMD | awk '{ print $3 }'`
C=`echo $CMD | awk '{ print $4 }'`
#IF Statement for comparing the three of them
#echo the smallest
done