Re-do of plot_quick

specutils/spectra/spectrum1d.py

@@ -768,3 +768,76 @@
         result = "<Spectrum1D({})>".format(inner_str)
 
         return result
+
+    def plot(self, ax=None, x_name='spectral axis', y_name='flux',
+                   set_quantity_support=True, **kwargs):
+        """
+        Visualize this spectrum using matplotlib in "histogram style".
+
+        Parameters
+        ----------
+        ax : `matplotlib.axes.Axes` or None
+            The axis to plot this figure into.  If None, use the current
+            ``pyplot`` axes (which will create a new figure if none exists).
+        x_name : str or None
+            The name to use for the x axis (units will be automatically added)
+            or None to not set the x axis label.
+        y_name : str or None
+            The name to use for the y axis (units will be automatically added)
+            or None to not set the y axis label.
+        set_quantity_support : bool
+            If True, call `astropy.visualization.quantity_support` to ensure
+            that the quantities in the plot are properly settable.
+
+        kwargs are passed into `~matplotlib.axes.Axes.plot`, except for
+        ``drawstyle`` or ``ds``.
+
+        Returns
+        -------
+        ax : `matplotlib.axes.Axes`
+            Either ``ax``, or the newly created axes object (if the ``ax``
+            parameter is None).
+        """
+        # import is intentionally inside the method to make matplotlib an
+        # "optional" dependency
+        from matplotlib import pyplot as plt
+        from astropy.visualization import quantity_support
+
+        if set_quantity_support:
+            quantity_support()
+
+        if 'drawstyle' in kwargs or 'ds' in kwargs:
+            raise TypeError("cannot set draw style in a spectrum's plot_quick")
+
+        kwargs['drawstyle'] = 'steps-post'
+
+        if len(self.shape) != 1:
+            nspecdim = len(self.shape) - 1
+            indexing_hint = 'spec[' + ', '.join(['0']*nspecdim) + ']'
+            raise ValueError(f'plot_quick can only be used on 1d spectra. To '
+                              'get the first spectrum, try {indexing_hint}')
+
+        if ax is None:
+            ax = plt.gca()
+
+        # TODO: replace below with self.bin_edges once it is correct
+        mid_bin_edges = (self.spectral_axis[1:] + self.spectral_axis[:-1])/2
+        bin_edges = np.concatenate([(self.spectral_axis[0]*2-mid_bin_edges[0]).ravel(),
+                                     mid_bin_edges,
+                                     (self.spectral_axis[-1]*2-mid_bin_edges[-1]).ravel()])
+
+        # for a plot with steps-post, the last horizontal line requires a repeat
+        # of the last flux value
+        extended_flux = np.concatenate([self.flux, [self.flux[-1]]])
+
+        ax.plot(bin_edges, extended_flux, **kwargs)
+
+        if x_name is not None:
+            sa_unit = self.spectral_axis.unit.to_string(format='latex_inline')
+            ax.set_xlabel(x_name + f' [{sa_unit}]')
+
+        if y_name is not None:
+            flux_unit = self.flux.unit.to_string(format='latex_inline')
+            ax.set_ylabel(y_name + f' [{flux_unit}]')
+
+        return ax

specutils/tests/test_spectrum1d.py

@@ -11,6 +11,12 @@
 from .conftest import remote_access
 from ..spectra import Spectrum1D
 
+try:
+    import matplotlib
+    HAS_MATPLOTLIB = True
+except ImportError:
+    HAS_MATPLOTLIB = False
+
 
 def test_empty_spectrum():
     spec = Spectrum1D(spectral_axis=[]*u.um,
@@ -538,3 +544,10 @@ def test_spectral_axis_direction():
     wave = [3, 2, 1] * u.nm
     spec1d = Spectrum1D(spectral_axis=wave, flux=flux)
     assert spec1d.spectral_axis_direction == 'decreasing'
+
+
+@pytest.mark.skipif('not HAS_MATPLOTLIB')
+def test_plot():
+    spec_single_flux = Spectrum1D([1, 2] * u.Jy, [3, 4] * u.nm)
+    ax = spec_single_flux.plot()
+    assert isinstance(ax, matplotlib.axes.Axes)