def install_pip(self, package, save=True, save_dev=False):
        """Installs a pip package.

        :param save: if `True`, pins the package to the Hydrogen requirements
            YAML file.
        :param save_dev: if `True`, pins the package as a development
            dependency to the Hydrogen requirements YAML file.
        :param return: a **single** :class:`Requirement` object, representing
            the installed version of the given package.
        """
        requirement = Requirement.coerce(package)
        click.echo("pip install " + requirement.package)
        cmd = envoy.run("pip install {}".format(str(requirement)))
        if cmd.status_code == 0:
            installed_packages = get_installed_pypackages()
            package = installed_packages[requirement.package]
            requirement.version = "=={}".format(package.version)
            if save:
                self.requirements["all"].add(requirement)
            if save_dev:
                self.requirements["dev"].add(requirement)
            if save or save_dev:
                self.requirements.save()
            return requirement
        else:
            fatal(cmd.std_err)
def torque(pos, torque, ax=0):
    """creates plot from torque vs position"""
    k = 20
    alpha = np.linspace(pos[0], pos[-1],
                        k*len(torque))
    f = ip.interp1d(pos, torque, kind='quadratic')
    unit = 'Nm'
    scale = 1
    if np.min(torque) < -9.9e3 or np.max(torque) > 9.9e3:
        scale = 1e-3
        unit = 'kNm'
    if ax == 0:
        ax = plt.gca()
    ax.set_title('Torque / {}'.format(unit))
    ax.grid(True)
    ax.plot(pos, [scale*t for t in torque], 'go')
    ax.plot(alpha, scale*f(alpha))
    if np.min(torque) > 0 and np.max(torque) > 0:
        ax.set_ylim(bottom=0)
    elif np.min(torque) < 0 and np.max(torque) < 0:
        ax.set_ylim(top=0)