Change Bar Color of Top-n values

Hi,

I want to create a vbar glyph in Bokeh with a different color on the top-n values.

I’m relatively new to Bokeh and I couln’t find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.

Here is a simple example with standard color:

from bokeh.plotting import figure
from bokeh.models import ColumnDataSource

data = {‘x_values’: [5,6,7,8,9],
‘y_values’: [1000, 2000, 2500, 1500, 1200]}

source = ColumnDataSource(data=data)

f = figure(plot_width=400, plot_height=600)

f.vbar(x=‘x_values’, top=‘y_values’, width=0.8, source=source)

show(f)

``

How could I change the color for the top2 values? I think it can’t be that difficult, but I’m searching for a solution for a long time now and still did not find any…

Thank you very much in advance,

Verena

Hi,

It's not apparent if you are looking to have this happen "automagically" or not. There is nothing built in to Bokeh to do it automatically. You can either:

* Set the colors yourself (and maybe this is what you are asking for?) i.e.

  from bokeh.plotting import figure
  from bokeh.models import ColumnDataSource

  data = {'x_values': [5,6,7,8,9],
          'y_values': [1000, 2000, 2500, 1500, 1200]
          'colors' : ['blue', 'red', 'red', blue', 'blue']}
        
  source = ColumnDataSource(data=data)
        
  f = figure(plot_width=400, plot_height=600)

  f.vbar(x='x_values', top='y_values', color='colors', width=0.8, source=source)

  show(f)

That will set the colors of the top 2 bars to "red", because I have explicitly told it to do so, i.e. told it myself which bars are the ones to shade differently.

* Alternatively, you could write a CustomJSTransform that shades the bars automatically in the browser:

  https://bokeh.pydata.org/en/latest/docs/reference/models/transforms.html#bokeh.models.transforms.CustomJSTransform

In this case you could write a bit of JavaScript code that returns any array of colors that you want based on the input column, i.e. it could return red for the top 2 or 3 and blue for everything else.

Bryan

···

On Sep 5, 2018, at 06:04, [email protected] wrote:

Hi,

I want to create a vbar glyph in Bokeh with a different color on the top-n values.

I'm relatively new to Bokeh and I couln't find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.

Here is a simple example with standard color:

from bokeh.plotting import figure
from bokeh.models import ColumnDataSource

data = {'x_values': [5,6,7,8,9],
        'y_values': [1000, 2000, 2500, 1500, 1200]}
        
source = ColumnDataSource(data=data)
        
f = figure(plot_width=400, plot_height=600)

f.vbar(x='x_values', top='y_values', width=0.8, source=source)

show(f)

How could I change the color for the top2 values? I think it can't be that difficult, but I'm searching for a solution for a long time now and still did not find any...

Thank you very much in advance,

Verena

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For more options, visit https://groups.google.com/a/continuum.io/d/optout.

Hi Bryan,

thank you very much for your support. It was the “automagically” way I was looking for. So I figured out a solution writing a CustomJSTransform. Since it was my first JavaScript-Code, there might be

more elegant ways to do it, but at least it worked for me. In case someone is also looking for this solution, here is my one:

from bokeh.models import ColumnDataSource, CustomJSTransform
from bokeh.plotting import figure
from bokeh.transform import transform

data = {‘x_values’: [5,6,7,8,9],
‘y_values’: [1000, 2000, 2500, 1500, 1200]}

source = ColumnDataSource(data=data)

color_transform = CustomJSTransform(args=dict(source=source), func="", v_func="""
var val = new Array(xs.length)
var color_array = new Array ();
for (var i = 0; i < xs.length; i++) {
if (source.data[‘y_values’][i] < Math.max(…source.data[‘y_values’].slice(0, 2))){
color_array.push(‘navy’)

    }
    else {
    color_array.push('deeppink')
   
    }
   
 
  }
return color_array

“”")

f = figure(plot_width=400, plot_height=600)

f.vbar(x=‘x_values’, top = ‘y_values’, width=0.8, source=source, fill_color = transform(‘y_values’, color_transform), line_color = transform(‘y_values’, color_transform))

``

top_n_example.png

Verena

···

On Tuesday, September 11, 2018 at 1:51:26 AM UTC+2, Bryan Van de ven wrote:

Hi,

It’s not apparent if you are looking to have this happen “automagically” or not. There is nothing built in to Bokeh to do it automatically. You can either:

  • Set the colors yourself (and maybe this is what you are asking for?) i.e.

      from bokeh.plotting import figure
    
      from bokeh.models import ColumnDataSource
    
    
    
      data = {'x_values': [5,6,7,8,9],
    
              'y_values': [1000, 2000, 2500, 1500, 1200]
    
              'colors'  : ['blue', 'red', 'red', blue', 'blue']}
    
     
      source = ColumnDataSource(data=data)
    
     
      f = figure(plot_width=400, plot_height=600)
    
    
    
      f.vbar(x='x_values', top='y_values', color='colors', width=0.8, source=source)
    
    
    
      show(f)
    

That will set the colors of the top 2 bars to “red”, because I have explicitly told it to do so, i.e. told it myself which bars are the ones to shade differently.

  • Alternatively, you could write a CustomJSTransform that shades the bars automatically in the browser:

      [https://bokeh.pydata.org/en/latest/docs/reference/models/transforms.html#bokeh.models.transforms.CustomJSTransform](https://bokeh.pydata.org/en/latest/docs/reference/models/transforms.html#bokeh.models.transforms.CustomJSTransform)
    

In this case you could write a bit of JavaScript code that returns any array of colors that you want based on the input column, i.e. it could return red for the top 2 or 3 and blue for everything else.

Bryan

On Sep 5, 2018, at 06:04, [email protected] wrote:

Hi,

I want to create a vbar glyph in Bokeh with a different color on the top-n values.

I’m relatively new to Bokeh and I couln’t find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.

Here is a simple example with standard color:

from bokeh.plotting import figure

from bokeh.models import ColumnDataSource

data = {‘x_values’: [5,6,7,8,9],

    'y_values': [1000, 2000, 2500, 1500, 1200]}

source = ColumnDataSource(data=data)

f = figure(plot_width=400, plot_height=600)

f.vbar(x=‘x_values’, top=‘y_values’, width=0.8, source=source)

show(f)

How could I change the color for the top2 values? I think it can’t be that difficult, but I’m searching for a solution for a long time now and still did not find any…

Thank you very much in advance,

Verena


You received this message because you are subscribed to the Google Groups “Bokeh Discussion - Public” group.

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To view this discussion on the web visit https://groups.google.com/a/continuum.io/d/msgid/bokeh/eb9e64a9-cead-4057-9cbb-4c9662ce4440%40continuum.io.

For more options, visit https://groups.google.com/a/continuum.io/d/optout.

Hi,

That's about what I had imagined, in outline. But FWIW think this if-test is not quite right

  if (source.data['y_values'][i] < Math.max(...source.data['y_values'].slice(0, 2))

And that if it that is working, it is only by accident. That is taking the max of the first three elements, but in general, there is no guarantee the overall max, or nth largest value is one of the first three values. I would expect you'd need to make a new sorted version of the input array, before the loop, and use that to pick out the n-th largest value.

Thanks,

Bryan

···

On Sep 11, 2018, at 05:59, [email protected] wrote:

Hi Bryan,

thank you very much for your support. It was the "automagically" way I was looking for. So I figured out a solution writing a CustomJSTransform. Since it was my first JavaScript-Code, there might be
more elegant ways to do it, but at least it worked for me. In case someone is also looking for this solution, here is my one:

from bokeh.models import ColumnDataSource, CustomJSTransform
from bokeh.plotting import figure
from bokeh.transform import transform

data = {'x_values': [5,6,7,8,9],
        'y_values': [1000, 2000, 2500, 1500, 1200]}
       
source = ColumnDataSource(data=data)

color_transform = CustomJSTransform(args=dict(source=source), func="", v_func="""
   var val = new Array(xs.length)
    var color_array = new Array ();
    for (var i = 0; i < xs.length; i++) {
        if (source.data['y_values'][i] < Math.max(...source.data['y_values'].slice(0, 2))){
            color_array.push('navy')
        
        }
        else {
        color_array.push('deeppink')
        
        }
        
      }
    return color_array
""")

f = figure(plot_width=400, plot_height=600)

f.vbar(x='x_values', top = 'y_values', width=0.8, source=source, fill_color = transform('y_values', color_transform),line_color = transform('y_values', color_transform))

<top_n_example.png>

Verena

On Tuesday, September 11, 2018 at 1:51:26 AM UTC+2, Bryan Van de ven wrote:
Hi,

It's not apparent if you are looking to have this happen "automagically" or not. There is nothing built in to Bokeh to do it automatically. You can either:

* Set the colors yourself (and maybe this is what you are asking for?) i.e.

        from bokeh.plotting import figure
        from bokeh.models import ColumnDataSource

        data = {'x_values': [5,6,7,8,9],
                'y_values': [1000, 2000, 2500, 1500, 1200]
                'colors' : ['blue', 'red', 'red', blue', 'blue']}
        
        source = ColumnDataSource(data=data)
        
        f = figure(plot_width=400, plot_height=600)

        f.vbar(x='x_values', top='y_values', color='colors', width=0.8, source=source)

        show(f)

That will set the colors of the top 2 bars to "red", because I have explicitly told it to do so, i.e. told it myself which bars are the ones to shade differently.

* Alternatively, you could write a CustomJSTransform that shades the bars automatically in the browser:

        https://bokeh.pydata.org/en/latest/docs/reference/models/transforms.html#bokeh.models.transforms.CustomJSTransform

In this case you could write a bit of JavaScript code that returns any array of colors that you want based on the input column, i.e. it could return red for the top 2 or 3 and blue for everything else.

Bryan

> On Sep 5, 2018, at 06:04, [email protected] wrote:
>
> Hi,
>
> I want to create a vbar glyph in Bokeh with a different color on the top-n values.
>
> I'm relatively new to Bokeh and I couln't find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.
>
> Here is a simple example with standard color:
>
> from bokeh.plotting import figure
> from bokeh.models import ColumnDataSource
>
> data = {'x_values': [5,6,7,8,9],
> 'y_values': [1000, 2000, 2500, 1500, 1200]}
>
> source = ColumnDataSource(data=data)
>
> f = figure(plot_width=400, plot_height=600)
>
> f.vbar(x='x_values', top='y_values', width=0.8, source=source)
>
> show(f)
>
>
> How could I change the color for the top2 values? I think it can't be that difficult, but I'm searching for a solution for a long time now and still did not find any...
>
> Thank you very much in advance,
>
> Verena
>
> --
> You received this message because you are subscribed to the Google Groups "Bokeh Discussion - Public" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
> To post to this group, send email to [email protected].
> To view this discussion on the web visit https://groups.google.com/a/continuum.io/d/msgid/bokeh/eb9e64a9-cead-4057-9cbb-4c9662ce4440%40continuum.io.
> For more options, visit https://groups.google.com/a/continuum.io/d/optout.

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For more options, visit https://groups.google.com/a/continuum.io/d/optout.
<top_n_example.png>

Hi Bryan,

thanks for your answer.

Of course you were right. I’m working with Pandas DataFrames and I sorted the df before now. I tested some examples and it seems to be working.

Or would you recommend to do the sorting inside the JS-part?

Thank you very much.

Verena

···

On Tuesday, September 11, 2018 at 1:42:51 AM UTC+2, [email protected] wrote:

Hi,

I want to create a vbar glyph in Bokeh with a different color on the top-n values.

I’m relatively new to Bokeh and I couln’t find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.

Here is a simple example with standard color:

from bokeh.plotting import figure
from bokeh.models import ColumnDataSource

data = {‘x_values’: [5,6,7,8,9],
‘y_values’: [1000, 2000, 2500, 1500, 1200]}

source = ColumnDataSource(data=data)

f = figure(plot_width=400, plot_height=600)

f.vbar(x=‘x_values’, top=‘y_values’, width=0.8, source=source)

show(f)

``

How could I change the color for the top2 values? I think it can’t be that difficult, but I’m searching for a solution for a long time now and still did not find any…

Thank you very much in advance,

Verena

Hi,

No, if you do know the data is sorted, then original code should be fine. I was just commenting that it's not true in general since it was not clear that it was true in your specific case.

Thanks,

Bryan

···

On Sep 28, 2018, at 09:35, [email protected] wrote:

Hi Bryan,

thanks for your answer.

Of course you were right. I'm working with Pandas DataFrames and I sorted the df before now. I tested some examples and it seems to be working.

Or would you recommend to do the sorting inside the JS-part?

Thank you very much.
Verena

On Tuesday, September 11, 2018 at 1:42:51 AM UTC+2, [email protected] wrote:
Hi,

I want to create a vbar glyph in Bokeh with a different color on the top-n values.

I'm relatively new to Bokeh and I couln't find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.

Here is a simple example with standard color:

from bokeh.plotting import figure
from bokeh.models import ColumnDataSource

data = {'x_values': [5,6,7,8,9],
        'y_values': [1000, 2000, 2500, 1500, 1200]}
        
source = ColumnDataSource(data=data)
        
f = figure(plot_width=400, plot_height=600)

f.vbar(x='x_values', top='y_values', width=0.8, source=source)

show(f)

How could I change the color for the top2 values? I think it can't be that difficult, but I'm searching for a solution for a long time now and still did not find any...

Thank you very much in advance,

Verena

--
You received this message because you are subscribed to the Google Groups "Bokeh Discussion - Public" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
To post to this group, send email to [email protected].
To view this discussion on the web visit https://groups.google.com/a/continuum.io/d/msgid/bokeh/4f98ece6-0839-4868-8455-3c7754230c32%40continuum.io.
For more options, visit https://groups.google.com/a/continuum.io/d/optout.

ok, thank you very much for your help!

Verena

···

On Tuesday, September 11, 2018 at 1:42:51 AM UTC+2, [email protected] wrote:

Hi,

I want to create a vbar glyph in Bokeh with a different color on the top-n values.

I’m relatively new to Bokeh and I couln’t find a solution which is working for me. The color mappers change the color according to a special range on the values, but I would like to define only e.g. the top 2 or top 3 values with a different color than the rest.

Here is a simple example with standard color:

from bokeh.plotting import figure
from bokeh.models import ColumnDataSource

data = {‘x_values’: [5,6,7,8,9],
‘y_values’: [1000, 2000, 2500, 1500, 1200]}

source = ColumnDataSource(data=data)

f = figure(plot_width=400, plot_height=600)

f.vbar(x=‘x_values’, top=‘y_values’, width=0.8, source=source)

show(f)

``

How could I change the color for the top2 values? I think it can’t be that difficult, but I’m searching for a solution for a long time now and still did not find any…

Thank you very much in advance,

Verena