Colorbar high limit is not always shown

Community Support
1

Hi,

I am struggeling to get the high limit for colorbars shown. It seems to be related to small values. In the example below with low limit 1.9 and high limit 2.3 the 2.3 is not shown. But if the high limit is 2.5 the the high limit is shown. If the values are 10 times higher the 23.0 is shown.

Or am I doing something wrong?

Kind regards,

Jonas

from bokeh.io import output_file, show
from bokeh.layouts import row
from bokeh.palettes import brewer
from bokeh.plotting import figure, ColumnDataSource
from bokeh.models import PrintfTickFormatter, LinearColorMapper, ColorBar

x = [1,2,3,4,5]
y = [1,10,100,1000,10000]
z1 = [1.82, 1.92, 2.03, 2.12, 2.24]
source1 = ColumnDataSource(
data = dict( x = x, y = y, z = z1))

z2 = [18.2, 19.2, 20.3, 21.2, 22.4]
source2 = ColumnDataSource(
data = dict( x = x, y = y, z = z2))

output_file(“colorbar.html”)

colors = brewer[“Spectral”][8]

mapper1 = LinearColorMapper(colors, low = 1.9, high = 2.3)
p1 = figure(width=350, height=300, y_axis_type = “log”,
toolbar_location=“above”)
p1.circle(x = ‘x’, y=‘y’, source = source1, size = 20,
color = {‘field’: ‘z’, ‘transform’: mapper1}, line_color = None)
color_bar1 = ColorBar(color_mapper=mapper1,
formatter = PrintfTickFormatter(format="%1.2f"),
label_standoff=12,
border_line_color=None,
location=(0,0))
p1.add_layout(color_bar1, ‘right’)

mapper2 = LinearColorMapper(colors, low = 1.9, high = 2.5)
p2 = figure(width=350, height=300, y_axis_type = “log”,
toolbar_location=“above”)
p2.circle(x = ‘x’, y=‘y’, source = source1, size = 20,
color = {‘field’: ‘z’, ‘transform’: mapper2}, line_color = None)
color_bar2 = ColorBar(color_mapper=mapper2,
formatter = PrintfTickFormatter(format="%1.2f"),
label_standoff=12,
border_line_color=None,
location=(0,0))
p2.add_layout(color_bar2, ‘right’)

mapper3 = LinearColorMapper(colors, low = 19, high = 23)
p3 = figure(width=350, height=300, y_axis_type = “log”,
toolbar_location=“above”)
p3.circle(x = ‘x’, y=‘y’, source = source2, size = 20,
color = {‘field’: ‘z’, ‘transform’: mapper3}, line_color = None)
color_bar3 = ColorBar(color_mapper=mapper3,
formatter = PrintfTickFormatter(format="%1.2f"),
label_standoff=12,
border_line_color=None,
location=(0,0))
p3.add_layout(color_bar3, ‘right’)

show(row([p1, p2, p3]))

2

Hi,

Be default, the ColorBar uses a "BasicTicker" which was originally written for plot axes, and tries to do something reasonable across a wide range of scales. But sometimes what it does is not what you want. In which case you'll want to resort to a different built-in ticker, e.g. FixedTicker:

  Appearance — Bokeh 3.3.2 Documentation

Or perhaps develop a custom extension ticker if your requirements are more specialized.

Thanks,

Bryan

···

On Feb 3, 2017, at 1:14 PM, Jonas Grave Kristensen <[email protected]> wrote:

Hi,

I am struggeling to get the high limit for colorbars shown. It seems to be related to small values. In the example below with low limit 1.9 and high limit 2.3 the 2.3 is not shown. But if the high limit is 2.5 the the high limit is shown. If the values are 10 times higher the 23.0 is shown.

Or am I doing something wrong?

Kind regards,
Jonas

<colorbar_high_limit.tiff>

from bokeh.io import output_file, show
from bokeh.layouts import row
from bokeh.palettes import brewer
from bokeh.plotting import figure, ColumnDataSource
from bokeh.models import PrintfTickFormatter, LinearColorMapper, ColorBar

x = [1,2,3,4,5]
y = [1,10,100,1000,10000]
z1 = [1.82, 1.92, 2.03, 2.12, 2.24]
source1 = ColumnDataSource(
   data = dict( x = x, y = y, z = z1))

z2 = [18.2, 19.2, 20.3, 21.2, 22.4]
source2 = ColumnDataSource(
   data = dict( x = x, y = y, z = z2))

output_file("colorbar.html")

colors = brewer["Spectral"][8]

mapper1 = LinearColorMapper(colors, low = 1.9, high = 2.3)
p1 = figure(width=350, height=300, y_axis_type = "log",
            toolbar_location="above")
p1.circle(x = 'x', y='y', source = source1, size = 20,
    color = {'field': 'z', 'transform': mapper1}, line_color = None)
color_bar1 = ColorBar(color_mapper=mapper1,
              formatter = PrintfTickFormatter(format="%1.2f"),
              label_standoff=12,
              border_line_color=None,
              location=(0,0))
p1.add_layout(color_bar1, 'right')

mapper2 = LinearColorMapper(colors, low = 1.9, high = 2.5)
p2 = figure(width=350, height=300, y_axis_type = "log",
            toolbar_location="above")
p2.circle(x = 'x', y='y', source = source1, size = 20,
    color = {'field': 'z', 'transform': mapper2}, line_color = None)
color_bar2 = ColorBar(color_mapper=mapper2,
              formatter = PrintfTickFormatter(format="%1.2f"),
              label_standoff=12,
              border_line_color=None,
              location=(0,0))
p2.add_layout(color_bar2, 'right')

mapper3 = LinearColorMapper(colors, low = 19, high = 23)
p3 = figure(width=350, height=300, y_axis_type = "log",
            toolbar_location="above")
p3.circle(x = 'x', y='y', source = source2, size = 20,
    color = {'field': 'z', 'transform': mapper3}, line_color = None)
color_bar3 = ColorBar(color_mapper=mapper3,
              formatter = PrintfTickFormatter(format="%1.2f"),
              label_standoff=12,
              border_line_color=None,
              location=(0,0))
p3.add_layout(color_bar3, 'right')

show(row([p1, p2, p3]))

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