Changing grid position in Bokeh

Question

I'm trying to make a table to represent the relationship between categorical values based on their count. This is my current code:

source = ColumnDataSource(df)
mapper = LinearColorMapper(palette=brewer['YlGnBu'][4], low=df['count'].min(), high=df['count'].max())
tooltips = [
    ("Resource", "@org:resoure"),
    ("Activity", "@concept:name"),
    ("Count", "@count"),
]
p = figure(plot_width=df['org:resource'].nunique()*180, plot_height=df['concept:name'].nunique()*100, title="US Unemployment 1948—2016",
           y_range=df['concept:name'].unique(), x_range=df['org:resource'].unique(),x_axis_location="above", tooltips=tooltips)

p.rect(y="concept:name", x="org:resource", width=1, height=1, source=source,
       line_color=None, fill_color=transform('count', mapper))

color_bar = ColorBar(color_mapper=mapper, location=(0, 0),
                     ticker=BasicTicker(),
                     formatter=PrintfTickFormatter(format="%d%%"))

p.add_layout(color_bar, 'right')

p.axis.axis_line_color = None
p.axis.major_tick_line_color = None
p.axis.major_label_text_font_size = "13px"
p.axis.major_label_standoff = 0
p.xaxis.major_label_orientation = 0

output_notebook()
show(p)

However, this code produces a grid that does not suite categorical values. How can I shift the grid down?

current visual produced by code

Answer 1

You can achieve this using a FixedTicker.

Here is a very basic example where p.rect() is used.

old	new

The code is very similar, except the ticks are shifted by 0.5 on both axis in the new version using the FixedTicker I mentioned.

old

from bokeh.plotting import figure, output_file, show

data = [1, 5]
plot = figure(plot_width=300, plot_height=300)
plot.rect(x=data, y=data, width=1, height=1, color="#CAB2D6")

show(plot)

new

from bokeh.plotting import figure, output_file, show
from bokeh.models import FixedTicker

data = [1, 5]
plot = figure(plot_width=300, plot_height=300)
plot.rect(x=data, y=data, width=1, height=1, color="#CAB2D6")

_max = max(data)
plot.xaxis.ticker = FixedTicker(ticks=[x+0.5 for x in range(_max+1)])
plot.yaxis.ticker = FixedTicker(ticks=[x+0.5 for x in range(_max+1)])

show(plot)