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Get the MAX value out of a column

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# 1  
Old 04-24-2013
Get the MAX value out of a column
I've the following data set. I would like to look at the column 3 and only use the rows which has the max value for column 3

Can we use the awk or sed to achieve it.

Code:
10      2       10       100
11      2       20       100
12      2       30       100
13      2       30       100
14      2       4       100
15      2       4       100
16      2       2       100
17      2       2       100
18      2       1       100

so based on the above data, max value for column 3 is 30. The results I would want is

Code:
12      2       30       100
13      2       30       100

# 2  
Old 04-24-2013
Code:
awk 'NR==FNR { if((!MAX)||(MAX<$3)) MAX=$3; next }; $3==MAX' filename filename

# 3  
Old 04-24-2013
Code:
awk '{A[NR" "$3]=$0;max=max<$3?$3:max}END{for(k in A){split(k,B);if(B[2]==max) print A[k]}} ' file

# 4  
Old 04-25-2013
While the OP's sample data consists exclusively of positive integers, if negative values and zeroes must be handled, neither solution is correct.

Corona's code will unconditionally set MAX to the next line's $3, if MAX is ever set to 0.
Code:
$ cat file
-1 -1 -1 -1
0 0 0 0
-2 -2 -2 -2
$ awk 'NR==FNR { if((!MAX)||(MAX<$3)) MAX=$3; next }; $3==MAX' file file
-2 -2 -2 -2
$ awk 'NR==FNR { if((NR==1)||(MAX<$3)) MAX=$3; next }; $3==MAX' file file
0 0 0 0

Yoda's code implicitly uses a max of 0 when NR==1 (a numeric 0 is the default value of an uninitialized variable). If that implicit 0, which is not present in the file, is greater than all values, B[2]==max will never succeed and no output is generated. max must be initialized from the first value of $3.
Code:
$ cat file
-1 -1 -1 -1
-2 -2 -2 -2
-3 -3 -3 -3
$ awk '{A[NR" "$3]=$0;max=max<$3?$3:max}END{for(k in A){split(k,B);if(B[2]==max) print A[k]}}' f
$ awk '{A[NR" "$3]=$0;max=max<$3||NR==1?$3:max}END{for(k in A){split(k,B);if(B[2]==max) print A[k]}}' f
-1 -1 -1 -1

Regards,
Alister
# 5  
Old 04-25-2013
Code:
$ awk '$3 == hi {print}' hi=$(awk '{print $3}' file | sort -n | tail -1) file
12      2       30       100
13      2       30       100

# 6  
Old 04-25-2013
Can be shorten some bye removing the print, since it's a default action.
Code:
awk '$3==hi' hi=$(awk '{print $3}' file | sort -n | tail -1) file

Other variation
Code:
awk '$3==hi' hi=$(awk '$3>n {n=$3} END {print n}' file) file
12      2       30       100
13      2       30       100

Last edited by Jotne; 04-25-2013 at 02:58 AM..
# 7  
Old 04-25-2013
Code:
$ sort -nr -k3,3 file|awk '$3<p{exit} {p=$3}1' 
13      2       30       100
12      2       30       100

To avoid the trap that alister pointed out, if negative values are expected in the file, preset p by adding p=$(getconf INT_MIN) to the end of the command.
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