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

[Chris Cormack]

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 at katipo.co.nz                                          www.katipo.co.nz