Yeh, I remembered that when I bombed out on a case with two samples so I have added a guard clause that I do not try to use LR if I have less than 10 samples. It appears to still have some very degenerate cases that kill this module with plenty of samples. I have now updated my code to divide Max(Y) by Min(Y) and use this 'change' value to alter the number of terms I use. Strangely it looks like cases where there is a sudden step change in the data that trigger this failure, I have one case where there is a 56% change and that kills the module.

    # Lets play with order based on Max/Min value
    my $change = $data->{Max}{AVG_Percentage_Used} / $data->{Min}{AVG_
+Percentage_Used};
    print "Change is $change\n";
    my $order = 1;
    $order = 2 if $change > 1.05;
    $order = 3 if $change > 1.15;
    $order = 4 if $change > 1.30;

    my @Thetas = 'Const'; # Set Thetas for zero order
    push @Thetas, 'Theta'.$_ for 1 .. $order;

    my $reg = Statistics::Regression->new( $data->{Name}, \@Thetas );

    # Add data points
    for ( @{$data->{values}} ) {
        my $epoch = mktime($s, $m, $h, $D, $M-1, $Y);
        my $x = $_->[2];
        my @Data = 1;
        push @Data, $x**$_ for 1..$order;
        print "\$reg->include ( $epoch, [".(join ", ", @Data)." ] )\n"
+;
        $reg->include ( $epoch, \@Data );
    }
    print "Results are ...\n";
    $reg->print();
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That appear to guard the cases where I had very little movement in Y over the series, but this one still kills it. The value 'Change' in this debug is Max/Min, so here there is a 30% change

Change is 1.3
$reg->include ( 1491859118, [1, 3.25, 10.5625 ] )
$reg->include ( 1491902520, [1, 3.25, 10.5625 ] )
$reg->include ( 1492032609, [1, 2.5, 6.25 ] )
$reg->include ( 1492117432, [1, 2.5, 6.25 ] )
$reg->include ( 1492204208, [1, 2.5, 6.25 ] )
$reg->include ( 1492291088, [1, 2.5, 6.25 ] )
$reg->include ( 1492377875, [1, 2.5, 6.25 ] )
$reg->include ( 1492464416, [1, 2.5, 6.25 ] )
$reg->include ( 1492551241, [1, 2.5, 6.25 ] )
$reg->include ( 1492623578, [1, 2.5, 6.25 ] )
Results are ...
****************************************************************
Regression 'gotsvl2143.dpcmsr1t.TOOLS'
****************************************************************
Report.pl::Statistics::Regression:standarderrors: I cannot compute the
+ theta-covariance matrix for variable 3 0
[download]

Cheers,
R.