sub create_chart {
    my ($ydata) = @_;
    Chart::Gnuplot::DataSet->new(
        xdata => \@yfix,
        ydata => $ydata,
        style => "lines",
        color => "dark-gray",
        linetype => "dash",
        width => 1,
    );
}

my $tempmin = create_chart(\@minit);
my $tempmax = create_chart(\@maxit);