Difficulty trying to change color mapper with the use of widgets

Community Support
1

Hello there,

I have been trying to switch between two different color mappers of patches with the use of widgets, but even trying to include a static color mapper as a part of a DataColumnSource fails triumphantly.

palettes = [pv_palette, wind_palette]

palette_dict = {‘palettes’:palettes}

palette_source = ColumnDataSource(data = palette_dict)

slider = Slider(title=None, start=0, end=len(date_avg_list)-1, step=1, value=0, show_value=False)

def callback(attr, old, new):

N = slider.value

source.data={‘x’:pv_capacity_merged[‘lons’],

‘y’: pv_capacity_merged[‘lats’],

‘monthly_avg’:pv_capacity_merged[date_avg_list[N]],

‘color_mapper’:pd.Series(516*[LinearColorMapper(palette=palette_source.data[‘palettes’][0],

low=return_source.data[‘lowest’][0],

high=return_source.data[‘highest’][0])])[1]

}

slider.on_change(‘value’, callback)

slider.on_change(‘value’, update_plot2)

p.patches(‘x’, ‘y’, source = source, fill_color={‘field’: ‘monthly_avg’, ‘transform’: ‘color_mapper’},

fill_alpha=0.7, line_color=“white”, line_width=0.5)

The above code should to my understanding load just one color mapper. The 516 is used just to have ColumnDataSource values of equal length.

Any ideas?

Thanks

2

Hi,

Your main issue is that ColorMappers do not go *in* data source columns. Rather, they represent of transformation *of* a column, and furthermore, this transformation happens in the browser, not in python. You can refer to this example to see the proper usage of LinearColorMapper:

  https://bokeh.pydata.org/en/latest/docs/gallery/unemployment.html

Depending on your use-case, the simpler bokeh.transforms.linear_cmap convenience function might also work. It is used like this, no need to make a LinearColorMapper by hand:

  fill_color=linear_cmap('colname', palette, min, max)

Thanks,

Bryan

···

On Mar 27, 2018, at 06:03, SinniK Al <[email protected]> wrote:

Hello there,

I have been trying to switch between two different color mappers of patches with the use of widgets, but even trying to include a static color mapper as a part of a DataColumnSource fails triumphantly.

palettes = [pv_palette, wind_palette]
palette_dict = {'palettes':palettes}
palette_source = ColumnDataSource(data = palette_dict)

slider = Slider(title=None, start=0, end=len(date_avg_list)-1, step=1, value=0, show_value=False)

def callback(attr, old, new):
    N = slider.value
    source.data={'x':pv_capacity_merged['lons'],
                 'y': pv_capacity_merged['lats'],
                 'monthly_avg':pv_capacity_merged[date_avg_list[N]],
                 'color_mapper':pd.Series(516*[LinearColorMapper(palette=palette_source.data['palettes'][0],
                                         low=return_source.data['lowest'][0],
                                         high=return_source.data['highest'][0])])[1]
                }
    
slider.on_change('value', callback)
slider.on_change('value', update_plot2)
p.patches('x', 'y', source = source, fill_color={'field': 'monthly_avg', 'transform': 'color_mapper'},
          fill_alpha=0.7, line_color="white", line_width=0.5)

The above code should to my understanding load just one color mapper. The 516 is used just to have ColumnDataSource values of equal length.
Any ideas?
Thanks

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