Random expansion of monthly data into daily data

convert-daily.ps1

# Random expansion of monthly data into daily data
# Syntax: convert-daily "c:\LokadData\foo.tsv" 
# Expected columns are Id, Date, Quantity
# By Joannes Vermorel, April 2016

function convert-daily
{
    param
    (
        [string] $file
    )

    # looking for the output path
    $path = [System.IO.Path]::GetDirectoryName($file);
    $output = [System.IO.Path]::GetFileNameWithoutExtension($file);
    $outext = [System.IO.Path]::GetExtension($file);

    $stream = [System.IO.StreamWriter] ($path + "\"+ $output + "-daily" + $outext);

    $r = ([random]42);
    $isFirst = $true;
    foreach ($line in [System.IO.File]::ReadLines($file))
    {
        if($isFirst) 
        {
            $isFirst = $false;
            $header = $line;
            $stream.WriteLine($header);
        }
        else
        {
            $tokens = $line.Split("`t");
            $id = $tokens[0];
            $dt = [datetime] $tokens[1];
            $qt = [int] $tokens[2];

            for($i = $qt; $i -gt 0; $i--)
            {
                $dti = $dt.AddDays($r.Next(30));
                $stream.WriteLine($id + "`t" + $dti.ToString("yyyy-MM-dd") + "`t1");
            }
        }
    }

    $stream.Close();
}