Awk script displaying incorrect output

Question

I'm facing an issue in awk script - I need to generate a report containing the lowest, highest and average score for each assignment in the data file. The name of the assignment is located in column 3.

Input data is:

Student,Catehory,Assignment,Score,Possible
Chelsey,Homework,H01,90,100
Chelsey,Homework,H02,89,100
Chelsey,Homework,H03,77,100
Chelsey,Homework,H04,80,100
Chelsey,Homework,H05,82,100
Chelsey,Homework,H06,84,100
Chelsey,Homework,H07,86,100
Chelsey,Lab,L01,91,100
Chelsey,Lab,L02,100,100
Chelsey,Lab,L03,100,100
Chelsey,Lab,L04,100,100
Chelsey,Lab,L05,96,100
Chelsey,Lab,L06,80,100
Chelsey,Lab,L07,81,100
Chelsey,Quiz,Q01,100,100
Chelsey,Quiz,Q02,100,100
Chelsey,Quiz,Q03,98,100
Chelsey,Quiz,Q04,93,100
Chelsey,Quiz,Q05,99,100
Chelsey,Quiz,Q06,88,100
Chelsey,Quiz,Q07,100,100
Chelsey,Final,FINAL,82,100
Chelsey,Survey,WS,5,5
Sam,Homework,H01,19,100
Sam,Homework,H02,82,100
Sam,Homework,H03,95,100
Sam,Homework,H04,46,100
Sam,Homework,H05,82,100
Sam,Homework,H06,97,100
Sam,Homework,H07,52,100
Sam,Lab,L01,41,100
Sam,Lab,L02,85,100
Sam,Lab,L03,99,100
Sam,Lab,L04,99,100
Sam,Lab,L05,0,100
Sam,Lab,L06,0,100
Sam,Lab,L07,0,100
Sam,Quiz,Q01,91,100
Sam,Quiz,Q02,85,100
Sam,Quiz,Q03,33,100
Sam,Quiz,Q04,64,100
Sam,Quiz,Q05,54,100
Sam,Quiz,Q06,95,100
Sam,Quiz,Q07,68,100
Sam,Final,FINAL,58,100
Sam,Survey,WS,5,5
Andrew,Homework,H01,25,100
Andrew,Homework,H02,47,100
Andrew,Homework,H03,85,100
Andrew,Homework,H04,65,100
Andrew,Homework,H05,54,100
Andrew,Homework,H06,58,100
Andrew,Homework,H07,52,100
Andrew,Lab,L01,87,100
Andrew,Lab,L02,45,100
Andrew,Lab,L03,92,100
Andrew,Lab,L04,48,100
Andrew,Lab,L05,42,100
Andrew,Lab,L06,99,100
Andrew,Lab,L07,86,100
Andrew,Quiz,Q01,25,100
Andrew,Quiz,Q02,84,100
Andrew,Quiz,Q03,59,100
Andrew,Quiz,Q04,93,100
Andrew,Quiz,Q05,85,100
Andrew,Quiz,Q06,94,100
Andrew,Quiz,Q07,58,100
Andrew,Final,FINAL,99,100
Andrew,Survey,WS,5,5
Ava,Homework,H01,55,100
Ava,Homework,H02,95,100
Ava,Homework,H03,84,100
Ava,Homework,H04,74,100
Ava,Homework,H05,95,100
Ava,Homework,H06,84,100
Ava,Homework,H07,55,100
Ava,Lab,L01,66,100
Ava,Lab,L02,77,100
Ava,Lab,L03,88,100
Ava,Lab,L04,99,100
Ava,Lab,L05,55,100
Ava,Lab,L06,66,100
Ava,Lab,L07,77,100
Ava,Quiz,Q01,88,100
Ava,Quiz,Q02,99,100
Ava,Quiz,Q03,44,100
Ava,Quiz,Q04,55,100
Ava,Quiz,Q05,66,100
Ava,Quiz,Q06,77,100
Ava,Quiz,Q07,88,100
Ava,Final,FINAL,99,100
Ava,Survey,WS,5,5
Shane,Homework,H01,50,100
Shane,Homework,H02,60,100
Shane,Homework,H03,70,100
Shane,Homework,H04,60,100
Shane,Homework,H05,70,100
Shane,Homework,H06,80,100
Shane,Homework,H07,90,100
Shane,Lab,L01,90,100
Shane,Lab,L02,0,100
Shane,Lab,L03,100,100
Shane,Lab,L04,50,100
Shane,Lab,L05,40,100
Shane,Lab,L06,60,100
Shane,Lab,L07,80,100
Shane,Quiz,Q01,70,100
Shane,Quiz,Q02,90,100
Shane,Quiz,Q03,100,100
Shane,Quiz,Q04,100,100
Shane,Quiz,Q05,80,100
Shane,Quiz,Q06,80,100
Shane,Quiz,Q07,80,100
Shane,Final,FINAL,90,100
Shane,Survey,WS,5,5

awk script :

BEGIN {
  FS=" *\\, *"
}

FNR>1 {
  min[$3]=(!($3 in min) || min[$3]> $4 )? $4 : min[$3]
  max[$3]=(max[$3]> $4)? max[$3] : $4
  cnt[$3]++
  sum[$3]+=$4
}
END {
  print "Name\tLow\tHigh\tAverage"
  for (i in cnt)
    printf("%s\t%d\t%d\t%.1f\n", i, min[i], max[i], sum[i]/cnt[i])

}

Expected sample output:

Name    Low     High    Average
Q06     77      95      86.80
L05     40      96      46.60
WS      5       5       5
Q07     58      100     78.80
L06     60      99      61
L07     77      86      64.80

When I run the script, I get a "Low" of 0 for all assignments which is not correct. Where am I going wrong? Please guide.

Answer 1

Your code works as-is with GNU awk. However, running it with the -t option to warn about non-portable constructs gives:

awk: foo.awk:6: warning: old awk does not support the keyword `in' except after `for'
awk: foo.awk:2: warning: old awk does not support regexps as value of `FS'

And running the script with a different implementation of awk (mawk in my case) does give 0's for the Low column. So, some tweaks to the script:

BEGIN {
  FS=","
}

FNR>1 {
  min[$3]=(cnt[$3] == 0 || min[$3]> $4 )? $4 : min[$3]
  max[$3]=(max[$3]> $4)? max[$3] : $4
  cnt[$3]++
  sum[$3]+=$4
}
END {
  print "Name\tLow\tHigh\tAverage"
  PROCINFO["sorted_in"] = "@ind_str_asc" # gawk-ism for pretty output; ignored on other awks
  for (i in cnt)
    printf("%s\t%d\t%d\t%.1f\n", i, min[i], max[i], sum[i]/cnt[i])

}

and it works as expected on that other awk too.

The changes:

• Using a simple comma as the field separator instead of a regex.
• Changing the min conditional to setting to the current value on the first time this assignment has been seen by checking to see if cnt[$3] is equal to 0 (Which it will be the first time because that value is incremented in a later line), or if the current min is greater than this value.

Answer 2

another similar approach

$ awk -F, 'NR==1 {print "name","low","high","average"; next} 
                 {k=$3; sum[k]+=$4; count[k]++}
     !(k in min) {min[k]=max[k]=$4} 
       min[k]>$4 {min[k]=$4} 
       max[k]<$4 {max[k]=$4}                    
       END       {for(k in min) print k,min[k],max[k],sum[k]/count[k]}' file | 
 column -t

name   low  high  average
Q06    77   95    86.8
L05    0    96    46.6
WS     5    5     5
Q07    58   100   78.8
L06    0    99    61
L07    0    86    64.8
H01    19   90    47.8
H02    47   95    74.6
H03    70   95    82.2