def freeze(h, output_yaml, resolve, groups):
    """Output installed packages."""
    if not groups:
        groups = filter(lambda group: not group.lower().startswith("bower"),
                        h.requirements.keys())
    else:
        groups = [text_type.strip(group) for group in groups.split(",")]

    if output_yaml:
        for requirements in h.requirements.values():
            for requirement in requirements:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
        click.echo(h.requirements.yaml)
    else:
        for group in groups:
            if not h.requirements[group]:
                continue
            click.echo("# {}".format(group))
            for requirement in h.requirements[group]:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
                click.echo(str(requirement))
def force_fft(order, force, ax=0):
    """plot force harmonics"""
    unit = 'N'
    scale = 1
    if min(force) < -9.9e3 or max(force) > 9.9e3:
        scale = 1e-3
        unit = 'kN'
    if ax == 0:
        ax = plt.gca()
    ax.set_title('Force Harmonics / {}'.format(unit))
    ax.grid(True)
    try:
        bw = 2.5E-2*max(order)
        ax.bar(order, [scale*t for t in force], width=bw, align='center')
        ax.set_xlim(left=-bw/2)
    except ValueError:  # empty sequence
        pass