Bokeh plot regression lines on scatter plot

Question

I generated two scatter plots in the same chart using Python and Bokeh, and added checkboxes to allow separate viewing of scatter plot.

How can I add regression lines for the two scatter plots (with equations) using Bokeh?

output_file("Scatterplot.html")

#scatter plot
S0 = f.circle(A_area, A_price,
         fill_alpha=0.3, size=3, color='green')
S1 = f.circle(B_area, B_price,
         fill_alpha=0.3, size=3, color='blue')

#widget-checkbox
checkboxes = CheckboxGroup(labels=["A", "B"], active=[0, 1])
callback = CustomJS(code="""S0.visible = false; // same S0 passed in from args
                            S1.visible = false;
                            // cb_obj injected in by the callback
                            if (cb_obj.active.includes(0)){S0.visible = true;} // 0 index box is S0
                            if (cb_obj.active.includes(1)){S1.visible = true;}""",
                    args={'S0': S0, 'S1': S1})

checkboxes.js_on_click(callback)

score 6 · Accepted Answer · answered Feb 09 '19 at 09:42

You calculate the line fit with numpy, and then you plot it in bokeh:

import numpy as np
from bokeh.plotting import figure
from bokeh.io import show

#the data
x=np.array([0,1,2,3,4,5,6,7,8])
y=np.array([1,2,3,5,4,6,8,7,9])

# determine best fit line
par = np.polyfit(x, y, 1, full=True)
slope=par[0][0]
intercept=par[0][1]
y_predicted = [slope*i + intercept  for i in x]

# plot it
fig=figure()
fig.circle(x,y)
fig.line(x,y_predicted,color='red',legend='y='+str(round(slope,2))+'x+'+str(round(intercept,2)))
show(fig)

score 4 · Answer 2 · answered Aug 23 '19 at 16:02

Bokeh also has a Slope class in their documentation for graphing a regression line like this. All you need is the intercept and slope to do so. Also, I'm using LinearRegression() from scikit-learn, but np.polyfit in Joris' answer obviously would work too.

import numpy as np
from sklearn.linear_model import LinearRegression
from bokeh.models import Slope
from bokeh.plotting import figure, show
from bokeh.io import output_notebook
output_notebook()

# Data
x=np.array([0,1,2,3,4,5,6,7,8])
y=np.array([1,2,3,5,4,6,8,7,9])

# Make and fit a linear regression model
model = LinearRegression().fit(x.reshape(-1, 1), y)
# x values need to be in a two-dimensional array, so use .reshape(-1, 1)

# Find the slope and intercept from the model
slope = model.coef_[0] # Takes the first element of the array
intercept = model.intercept_

# Make the regression line
regression_line = Slope(gradient=slope, y_intercept=intercept, line_color="red")

# Plot the data and regression line
fig=figure()
fig.circle(x, y)
fig.add_layout(regression_line)
show(fig)

If you want a line to run the full extent of the plot, rather than ending where the x-range ends, this is a better option than the accepted answer — kmt, Dec 09 '19 at 11:51

Bokeh plot regression lines on scatter plot

2 Answers2