Allow specifying grid

Author: ahuang11

doc/ref/plotting_options/styling.ipynb

@@ -311,6 +311,30 @@
     "plot2 = df.hvplot(group_label=\"Company\", grid=True, width=400, title=\"grid=True\")\n",
     "(plot1 + plot2).cols(1)"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "56cdf3e2",
+   "metadata": {},
+   "source": [
+    "To show grid only on the x-axis, use ``grid='x'``. To show grid only on the y-axis, use ``grid='y'``. To change the grid line style, suffix with ``'dashed'``, ``'dotted'``, ``'dotdash'``, or ``'dashdot'``, e.g. ``grid='x-dashed'``."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "7e38dee4",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import hvplot.pandas  # noqa\n",
+    "\n",
+    "df = hvplot.sampledata.stocks(\"pandas\", engine_kwargs={\"index_col\" : \"date\"})\n",
+    "\n",
+    "plot1 = df.hvplot(group_label=\"Company\", grid='x', width=400, title=\"grid='x'\")\n",
+    "plot2 = df.hvplot(group_label=\"Company\", grid='y-dashed', width=400, title=\"grid='y-dashed'\")\n",
+    "(plot1 + plot2).cols(1)"
+   ]
   }
  ],
  "metadata": {

hvplot/converter.py

@@ -475,8 +475,11 @@ class HoloViewsConverter:
     fontsize : number or dict or None, default=None
         Set title, label and legend text to the same fontsize. Finer control
         by using a dict: ``{'title': '15pt', 'ylabel': '5px', 'ticks': 20}``.
-    grid : bool or None, default=None
-        Whether to show a grid.
+    grid : bool, str, or None, default=None
+        Whether to show a grid. If True, shows grid on both axes.
+        If ``'x'`` or ``'y'``, shows grid only on the specified axis.
+        Suffix with ``'dashed'``, ``'dotted'``, ``'dotdash'``, or ``'dashdot'``
+        to change the grid line style, e.g. ``'x-dashed'``.
 
     Resampling Options
     ------------------
@@ -1059,7 +1062,16 @@ def __init__(
             plot_opts['logy'] = logy
 
         if grid is not None:
-            plot_opts['show_grid'] = grid
+            if isinstance(grid, str):
+                gridstyle = {}
+                axis = grid[0]
+                other_axis = 'x' if axis == 'y' else 'y'
+                if len(grid) > 0:
+                    line_dash = grid[1:].lstrip('-').lstrip('.').lstrip('_')
+                    gridstyle[f'{axis}grid_line_dash'] = line_dash
+                gridstyle[f'{other_axis}grid_line_alpha'] = 0
+                plot_opts['gridstyle'] = gridstyle
+            plot_opts['show_grid'] = bool(grid)
 
         if legend is not None:
             plot_opts['show_legend'] = bool(legend)

hvplot/tests/testoptions.py

@@ -635,6 +635,31 @@ def test_legend_opts(self, df, backend):
         opts = Store.lookup_options(backend, plot, 'plot')
         assert opts.kwargs['legend_opts'] == lo
 
+    @pytest.mark.parametrize('grid_bool', [True, False])
+    def test_grid_boolean(self, df, backend, grid_bool):
+        plot = df.hvplot('x', 'y', grid=grid_bool)
+        opts = Store.lookup_options(backend, plot, 'plot')
+        assert opts.kwargs['grid'] is grid_bool
+
+    def test_grid_x(self, df, backend):
+        plot = df.hvplot('x', 'y', grid='x')
+        opts = Store.lookup_options(backend, plot, 'plot')
+        assert opts.kwargs['grid'] is True
+        assert opts.kwargs['gridstyle'] == {'ygrid_line_alpha': 0}
+
+    def test_grid_y(self, df, backend):
+        plot = df.hvplot('x', 'y', grid='y')
+        opts = Store.lookup_options(backend, plot, 'plot')
+        assert opts.kwargs['grid'] is True
+        assert opts.kwargs['gridstyle'] == {'xgrid_line_alpha': 0}
+
+    @pytest.mark.parameterize('grid_str', ['x-dashed', 'xdashed', 'x.dashed', 'x_dashed'])
+    def test_grid_line_dash(self, df, backend, grid_str):
+        plot = df.hvplot('x', 'y', grid=grid_str)
+        opts = Store.lookup_options(backend, plot, 'plot')
+        assert opts.kwargs['grid'] is True
+        assert opts.kwargs['gridstyle'] == {'ygrid_line_alpha': 0, 'xgrid_line_dash': 'dashed'}
+
 
 @pytest.fixture(scope='module')
 def da():