Bokeh colormapping fixes (#1484)

* Fixed bug colormapping BarPlot

* Accept list of colors in place of bokeh cmap

* Add support for explicit cmap colors and bokeh palettes

* Add fix for BarPlot color field sanitization

holoviews/plotting/bokeh/chart.py

@@ -751,11 +751,11 @@ def get_data(self, element, ranges, empty):
 
         # Get colors
         cdim = color_dim or group_dim
-        cvals = element.dimension_values(cdim) if cdim else None
+        cvals = element.dimension_values(cdim, expanded=False) if cdim else None
         if cvals is not None:
             if cvals.dtype.kind in 'if' and no_cidx:
                 cvals = categorize_array(cvals, group_dim)
-            factors = None if cvals.dtype.kind in 'if' else list(np.unique(cvals))
+            factors = None if cvals.dtype.kind in 'if' else list(cvals)
             if cdim is xdim and factors:
                 factors = list(categorize_array(factors, xdim))
             if cmap is None and factors:
@@ -833,6 +833,8 @@ def get_data(self, element, ranges, empty):
         for name, val in mapping.items():
             if isinstance(val, basestring):
                 mapping[name] = dimension_sanitizer(mapping[name])
+            elif isinstance(val, dict) and 'field' in val:
+                val['field'] = dimension_sanitizer(val['field'])
 
         # Ensure x-values are categorical
         xname = dimension_sanitizer(xdim.name)

holoviews/plotting/bokeh/element.py

@@ -5,6 +5,7 @@
 import numpy as np
 import bokeh
 import bokeh.plotting
+from bokeh import palettes
 from bokeh.core.properties import value
 from bokeh.models import  HoverTool, Renderer, Range1d, DataRange1d, FactorRange
 from bokeh.models.tickers import Ticker, BasicTicker, FixedTicker, LogTicker
@@ -1013,7 +1014,21 @@ def _get_colormapper(self, dim, element, ranges, style, factors=None, colors=Non
         if colors:
             palette = colors
         else:
-            palette = mplcmap_to_palette(style.pop('cmap', 'viridis'), ncolors)
+            cmap = style.pop('cmap', 'viridis')
+            if isinstance(cmap, list):
+                palette = cmap
+            else:
+                try:
+                    # Process as matplotlib colormap
+                    palette = mplcmap_to_palette(cmap, ncolors)
+                except ValueError:
+                    # Process as bokeh palette
+                    palette = getattr(palettes, cmap, None)
+                    if isinstance(palette, dict):
+                        if ncolors in palette:
+                            palette = palette[ncolors]
+                        else:
+                            palette = sorted(palette.items())[-1][1]
         nan_colors = {k: rgba_tuple(v) for k, v in self.clipping_colors.items()}
         colormapper, opts = self._get_cmapper_opts(low, high, factors, nan_colors)