Re: [Koha-devel] To Chris : Problem on Loan Period calculation

7 Mar 2005

      On Wed, Mar 02, 2005 at 06:46:23PM +0100, Henri-Damien LAURENT said:
...
Hi,
We are trying to design a stat report module for Koha here in France 
with Paul.
And we have a problem on issues stats reporting.
In issues table, timestamp is modified as soon as the table is touched 
and returndate stores the date of return.
The issue date is never stored in this table anywhere else.
Nevertheless, it is stored in statistics. And returns are also stored there.
But then, there is no way to know how they are related to one another. A 
selection on itemnumber and borrower card will tell us it was issued and 
return, but not Which returns answers Which issue.
Suppose One borrows an item more than once and we are lost.
If one has a convenient code to know the average Loan period, that is a 
way to calculate the average time between issue and return date of an 
item for a borrower, we would be grateful.
You can work out the issue date by looking at the date_due field in issues.
And subtracting the loan period from it. Checking the renewals column also,
as if this is 1 say, the item has been renewed once .. so the original issue
date will be date_due - ( 2 * loan period)

using the Date::Manip module you can do this quite easily.

code snippet off the top of my head (beware probably full of syntax errors)

use Date::Manip;

my $query = "SELECT * FROM issues WHERE <some condition here>";
my $sth = $dbh->prepare($query);
$sth->execute;
my $total;
my $number_of_issues=0;
while (my $data = $sth->fetchrow_hashref()){
   my $due_date=ParseDate($data->{'date_due'});
   my $renewals=$data->{'renewals'};
   # probably need to do a select on the itemnumber to find what itemtype it
   # is and thus what loan period, ill pretend they are all the same for now
   my $loanperiod=21;
   $renewals++; # if null now equals 1
   my $loanlength=$loanperiod * $renewals;
   $issuedate = DateCalc($due_date,"- $loanlength days ago");
   my $returndate=ParseDate($data->{'retundate'});
   $delta = DateCalc($returndate,$issuedate,\$err);
   #  => 0:0:WK:DD:HH:MM:SS   the weeks, days, hours, minutes,
   #  and seconds between the two
   $number_of_issues++;
   # do something to the delta to just get the days say
   $total += $delta;
}
$sth->finish;
my $average = $total/$num_of_issues;

Something like that anyway :)

Hope this is some help

Chris
-- 
Chris Cormack                                                     Programmer
027 4500 789                                       Katipo Communications Ltd
chris@katipo.co.nz                                          www.katipo.co.nz