1D line plot with data on both axes + errorbar plotting added

xarray/plot/plot.py

@@ -20,7 +20,6 @@
 from .facetgrid import FacetGrid
 from xarray.core.pycompat import basestring
 
-
 def _valid_numpy_subdtype(x, numpy_types):
     """
     Is any dtype from numpy_types superior to the dtype of x?
@@ -164,6 +163,10 @@ def line(darray, *args, **kwargs):
     ----------
     darray : DataArray
         Must be 1 dimensional
+    x : string, optional
+        Coordinate for x axis. If None and y not None: 1D plot vertically oriented.
+    y : string, optional
+        Coordinate for y axis. If None: 1D plot horizontally oriented.
     figsize : tuple, optional
         A tuple (width, height) of the figure in inches.
         Mutually exclusive with ``size`` and ``ax``.
@@ -193,28 +196,138 @@ def line(darray, *args, **kwargs):
     aspect = kwargs.pop('aspect', None)
     size = kwargs.pop('size', None)
     ax = kwargs.pop('ax', None)
+    x = kwargs.pop('x', None)
+    y = kwargs.pop('y', None)
 
-    ax = get_axis(figsize, size, aspect, ax)
-
-    xlabel, = darray.dims
-    x = darray.coords[xlabel]
+    ax = get_axis(figsize, size, aspect, ax)    
 
-    _ensure_plottable(x)
+    #if isinstance(darray, DataArray):
+    if y != None:
+        y_arr = darray.coords[y]
+        _ensure_plottable(y_arr)
+        primitive = ax.plot(darray, y_arr, *args, **kwargs)
+        ax.set_ylabel(y)
+    else:
+        if x != None:
+            x_arr = darray.coords[x]
+            _ensure_plottable(x_arr)
+            primitive = ax.plot(x_arr, darray, *args, **kwargs)
+            ax.set_xlabel(x)
+        else:
+            xlabel, = darray.dims
+            x_arr = darray.coords[xlabel]
+            _ensure_plottable(x_arr)        
+            primitive = ax.plot(x_arr, darray, *args, **kwargs)
+            ax.set_xlabel(xlabel)
+
+        # Rotate dates on xlabels
+        if np.issubdtype(x_arr.dtype, np.datetime64):
+            plt.gcf().autofmt_xdate()
+
+    """
+    elif isinstance(darray, Dataset):
+        if x != None and y != None:
+            xval = darray[x].values
+            yval = darray[y].values
+            _ensure_plottable(xval, yval)
+            primitive = ax.plot(xval, yval, *args, **kwargs)
+            ax.set_xlabel(darray[x].name)
+            ax.set_ylabel(darray[y].name)
+        else:
+            raise ValueError('Two variables are necessary to lineplot Dataset')   
+
 
-    primitive = ax.plot(x, darray, *args, **kwargs)
+    else:
+        raise ValueError('Only DataArray and Dataset is acceptable')   
 
-    ax.set_xlabel(xlabel)
+    """
     ax.set_title(darray._title_for_slice())
 
     if darray.name is not None:
-        ax.set_ylabel(darray.name)
-
-    # Rotate dates on xlabels
-    if np.issubdtype(x.dtype, np.datetime64):
-        plt.gcf().autofmt_xdate()
+        if y != None:
+            ax.set_xlabel(darray.name)
+        else:
+            ax.set_ylabel(darray.name)    
 
     return primitive
 
+def errorbar(darray, *args, **kwargs):
+    """
+    Errorbar plot of 1 dimensional DataArray index against values
+
+    Wraps matplotlib.pyplot.plot
+
+    Parameters
+    ----------
+    darray : DataArray
+        Must be 1 dimensional
+    x : string, optional
+        Coordinate for x axis. If None and y not None: 1D plot vertically oriented.
+    y : string, optional
+        Coordinate for y axis. If None: 1D plot horizontally oriented.
+    figsize : tuple, optional
+        A tuple (width, height) of the figure in inches.
+        Mutually exclusive with ``size`` and ``ax``.
+    aspect : scalar, optional
+        Aspect ratio of plot, so that ``aspect * size`` gives the width in
+        inches. Only used if a ``size`` is provided.
+    size : scalar, optional
+        If provided, create a new figure for the plot with the given size.
+        Height (in inches) of each plot. See also: ``aspect``.
+    ax : matplotlib axes object, optional
+        Axis on which to plot this figure. By default, use the current axis.
+        Mutually exclusive with ``size`` and ``figsize``.
+    *args, **kwargs : optional
+        Additional arguments to matplotlib.pyplot.plot
+
+    """
+    plt = import_matplotlib_pyplot()
+    ndims = len(darray.dims)
+    if ndims != 1:
+        raise ValueError('Line plots are for 1 dimensional DataArrays. '
+                         'Passed DataArray has {ndims} '
+                         'dimensions'.format(ndims=ndims))
+
+    # Ensures consistency with .plot method
+    figsize = kwargs.pop('figsize', None)
+    aspect = kwargs.pop('aspect', None)
+    size = kwargs.pop('size', None)
+    ax = kwargs.pop('ax', None)
+    x = kwargs.pop('x', None)
+    y = kwargs.pop('y', None)
+
+    ax = get_axis(figsize, size, aspect, ax)    
+
+    #if isinstance(darray, DataArray):
+    if y != None:
+        y_arr = darray.coords[y]
+        _ensure_plottable(y_arr)
+        primitive = ax.errorbar(darray, y_arr.values, *args, **kwargs)
+        ax.set_ylabel(y)
+    else:
+        if x != None:
+            x_arr = darray.coords[x]
+            _ensure_plottable(x_arr)
+            primitive = ax.errorbar(x_arr.values, darray, *args, **kwargs)
+            ax.set_xlabel(x)
+        else:
+            xlabel, = darray.dims
+            x_arr = darray.coords[xlabel]
+            _ensure_plottable(x_arr)        
+            primitive = ax.errorbar(x_arr.values, darray, *args, **kwargs)
+            ax.set_xlabel(xlabel)
+
+        # Rotate dates on xlabels
+        if np.issubdtype(x_arr.dtype, np.datetime64):
+            plt.gcf().autofmt_xdate()
+
+    if darray.name is not None:
+        if y != None:
+            ax.set_xlabel(darray.name)
+        else:
+            ax.set_ylabel(darray.name)    
+
+    return primitive
 
 def hist(darray, figsize=None, size=None, aspect=None, ax=None, **kwargs):
     """
@@ -301,6 +414,9 @@ def hist(self, ax=None, **kwargs):
     def line(self, *args, **kwargs):
         return line(self._da, *args, **kwargs)
 
+    @functools.wraps(errorbar)
+    def errorbar(self, *args, **kwargs):
+        return errorbar(self._da, *args, **kwargs)
 
 def _plot2d(plotfunc):
     """