Awk script displaying incorrect output

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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.

awk scripting
3 Answers

You can certainly do this with awk, but since you tagged this scripting as well, I'm assuming other tools are an option. For this sort of gathering of statistics on groups present in the data, GNU datamash often reduces the job to a simple one-liner. For example: 

$ (echo Name,Low,High,Average; datamash --header-in -s -t, -g3 min 4 max 4 mean 4  < input.csv) | tr , '\t'
Name    Low     High    Average
FINAL   58      99      85.6
H01     19      90      47.8
H02     47      95      74.6
H03     70      95      82.2
H04     46      80      65
H05     54      95      76.6
H06     58      97      80.6
H07     52      90      67
L01     41      91      75
L02     0       100     61.4
L03     88      100     95.8
L04     48      100     79.2
L05     0       96      46.6
L06     0       99      61
L07     0       86      64.8
Q01     25      100     74.8
Q02     84      100     91.6
Q03     33      100     66.8
Q04     55      100     81
Q05     54      99      76.8
Q06     77      95      86.8
Q07     58      100     78.8
WS      5       5       5

This says that for each group with the same value for the 3rd column (-g3, plus -s to sort the input (A requirement of the tool)) of simple CSV input (-t,) with a header (--header-in), display the minimum, maximum, and mean of the 4th column. It's all given a new header and piped to tr to turn the commas into tabs.

user_99521960

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.
user_99521960

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
user_14358690
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