Unix Programming - Datafile Manipulation

Author

Datafile Manipulation

Adam

2006-02-17, 10:40 pm

Hi,
I'm trying to write a shell which will assess a list of student's
grades. The data file consists of the following...

2068344
8
6
3
8
2
8
2068943
9
7
3
7
3
7

The large numbers being the student ID, the small numbers being the
mark on a certain question.

My overall target is to output the student ID and the overall
percentage.
i.e.
2068344 78%
2068943 47%

I have run into a problem in that when performing the mathematics on
the file (at this stage the addition of the marks, leading to working
out the percentage), I can not dfferentiate between each individual
student, leaving me with one very large and useless number.

Any help on the matter would be brilliant.

Thank you.

Roger Leigh

2006-02-17, 10:40 pm

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Hash: SHA1

"Adam" <adamsalisbury@gmail.com> writes:

> 2068344
> 8
> 6
> 3
> 8
> 2
> 8
> 2068943
> 9
> 7
> 3
> 7
> 3
> 7
>
> The large numbers being the student ID, the small numbers being the
> mark on a certain question.

> I have run into a problem in that when performing the mathematics on
> the file (at this stage the addition of the marks, leading to working
> out the percentage), I can not dfferentiate between each individual
> student, leaving me with one very large and useless number.

We don't do homework questions here. However, one fairly obvious
observation is that there are two kinds of numbers, the 7-digit
student ID and the marks. Perhaps your shell script should
differentiate between them, and do something when it sees a new
student ID or the end of the file (like, say, a calculation).

Regards,
Roger

- --
Roger Leigh
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Pascal Bourguignon

2006-02-17, 10:40 pm

"Adam" <adamsalisbury@gmail.com> writes:

> Hi,
> I'm trying to write a shell which will assess a list of student's
> grades. The data file consists of the following...
>
> 2068344
> 8
> 6
> 3
> 8
> 2
> 8
> 2068943
> 9
> 7
> 3
> 7
> 3
> 7
>
> The large numbers being the student ID, the small numbers being the
> mark on a certain question.
>
> My overall target is to output the student ID and the overall
> percentage.
> i.e.
> 2068344 78%
> 2068943 47%
>
> I have run into a problem in that when performing the mathematics on
> the file (at this stage the addition of the marks, leading to working
> out the percentage), I can not dfferentiate between each individual
> student, leaving me with one very large and useless number.

It would be smarter to use awk rather than the shell.

$ awk '
BEGIN{student=0;maxmark=10;}
function report_student(){
if(student!=0){printf "%s %4.1f%%\n",student,total/nummark;}}
/[0-9][0-9][0-9]/{report_student(); student=$0; total=0;nummark=0; next;}
{total+=100.0*$0/maxmark; nummark++;}
END{report_student();}' <<EOF
2068344
8
6
3
8
2
8
2068943
9
7
3
7
3
7
EOF

2068344 58.3%
2068943 60.0%

--
__Pascal Bourguignon__ http://www.informatimago.com/

Nobody can fix the economy. Nobody can be trusted with their finger
on the button. Nobody's perfect. VOTE FOR NOBODY.

toby

2006-02-17, 10:40 pm

Pascal Bourguignon wrote:
> "Adam" <adamsalisbury@gmail.com> writes:
>
>
> It would be smarter to use awk rather than the shell.
>
> $ awk '
> BEGIN{student=0;maxmark=10;}
> function report_student(){
> if(student!=0){printf "%s %4.1f%%\n",student,total/nummark;}}
> /[0-9][0-9][0-9]/{report_student(); student=$0; total=0;nummark=0; next;}
> {total+=100.0*$0/maxmark; nummark++;}
> END{report_student();}' <<EOF
> 2068344
> 8
> 6
> 3
> 8
> 2
> 8
> 2068943
> 9
> 7
> 3
> 7
> 3
> 7
> EOF

Pascal, I'm not sure you'd have passed the assignment :-)

Here's a bash version; but since it is clearly homework, I have left
three deliberate errors in it: Two fairly easy, and one (thanks to
bash's quirks) fiendishly obscure. Printing one decimal place left as a
further exercise

#!/bin/bash

MAXMARK=10
printtot() {
local AVG
let AVG=(TOT*100)/(GRADES*MAXMARK)
echo "$NUM: $GRADES grades totalled $TOT = $AVG%"
}

while read VALUE ; do
if (( VALUE > MAXMARK )) ; then
if (( NUM )) ; then printtot ; fi
NUM= $VALUE
# reset for next student
TOT=0
GRADES=0
else
let TOT+=VALUE
let +GRADES
fi
done
printtot

Here's the result of the corrected script:

$ ./grades.sh <input
2068344: 6 grades totalled 35 = 58%
2068943: 6 grades totalled 36 = 60%
$

>
> 2068344 58.3%
> 2068943 60.0%
>
> --
> __Pascal Bourguignon__ http://www.informatimago.com/
>
> Nobody can fix the economy. Nobody can be trusted with their finger
> on the button. Nobody's perfect. VOTE FOR NOBODY.

William James

2006-02-20, 2:48 am

Adam wrote:
> Hi,
> I'm trying to write a shell which will assess a list of student's
> grades. The data file consists of the following...
>
> 2068344
> 8
> 6
> 3
> 8
> 2
> 8
> 2068943
> 9
> 7
> 3
> 7
> 3
> 7
>
> The large numbers being the student ID, the small numbers being the
> mark on a certain question.
>
> My overall target is to output the student ID and the overall
> percentage.
> i.e.
> 2068344 78%
> 2068943 47%
>
> I have run into a problem in that when performing the mathematics on
> the file (at this stage the addition of the marks, leading to working
> out the percentage), I can not dfferentiate between each individual
> student, leaving me with one very large and useless number.
>
> Any help on the matter would be brilliant.
>
> Thank you.

Ruby:

Max_score = 10
a = []
while s=gets
if s =~ /\d{7}/
a << [ s.strip ]
else
a.last << s.to_f
end
end
a.each{ |x|
printf "%s %0.1f%%\n", x.shift,
x.inject{|sum,i|sum + i}/(Max_score*x.size)*100
}