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 phasor(bch, ax=0):
    """create phasor plot from bch"""
    f1 = bch.machine['p']*bch.dqPar['speed']
    w1 = 2*np.pi*f1
    xd = w1*bch.dqPar['ld'][-1]
    xq = w1*bch.dqPar['lq'][-1]
    r1 = bch.machine['r1']
    i1beta_phasor(bch.dqPar['up'][-1],
                  bch.dqPar['i1'][-1], bch.dqPar['beta'][-1],
                  r1, xd, xq, ax)