[Arjen Markus] (13 january 2003) I have been experimenting with Metakit
as a convenient package to store measurement data (of course this was
the original design goal of Metakit, as [Jean-Claude Wippler] has
told me), but still getting some feeling for working with such a
database pacakge is worthwhile.

The script below (slightly adapted from the original) creates a
database from a simple data file and does some basic statistical
analysis.

The performance is quite acceptable to me:

The platform:

   Intel Pentium II, 350 MHz
   Windows 98
   tclkit, downloaded 3 july 2002 

The data file:

   Simple text file, 1.7 MB
   44000 lines each containing 9 integers

The results:

   11 seconds for reading the data file and creating the database
   11 seconds for retrieving 4 columns of 44000 data each and
      determining basic statistical properties
   resulting database is 0.9 MB
   about 80 lines of code

----

 # testdata.tcl --
 #
 #    Create a Metakit database and perform some simple statistical
 #    tests
 #
 # version 0.1: initial implementation, january 2003

 package require Mk4tcl
 source statistics.tcl

 # fillDatabase
 #    Fill the database with the contents of a tabular file
 #
 # Arguments:
 #    db       Opened database
 #    input    Name of the input file
 #
 # Result:
 #    Name of table (view) that was created
 #
 proc fillDatabase { db input } {

    set table [mk::view layout $db.table \
       {date a:F b:F c:F d:F}]

    set infile [open $input "r"]

    # Skip header
    gets $infile line

    while { [gets $infile line] > -1 } {
       foreach {dummy yy mm dd hh a b c d} $line {break}
       set date [format "19%2.2d%2.2d%2.2d%2.2d" $yy $mm $dd $hh]

       mk::row append $table date $date a $a \
                             b $b c $c d $d
    }
    close $infile

    mk::file commit $db

    return $table
 }

 # getColumn --
 #    Return a list consisting of the given column
 #
 # Arguments:
 #    table    Table or view to retrieve
 #    colname  Name of the column
 #
 # Results:
 #    List of values
 #
 proc getColumn { table colname } {
    set result {}
    mk::loop c $table {
      lappend result [mk::get $c $colname]
    }

    return $result
 }

 # main --
 #    Main code
 #

 console show

 mk::file open db "mydata.tkd"
 set table [fillDatabase db [file join .. "myfile.dat"]]
 set table "db.table"
 foreach col {a b c d} {
    set result [getColumn $table $col]
    puts "$col: [::math::statistics::basicStats $result]"
 }
 mk::file close db