Add trend line to pandas

Question

I have time-series data, as followed:

                  emplvl
date                    
2003-01-01  10955.000000
2003-04-01  11090.333333
2003-07-01  11157.0         


        

Answer 1

In general you should create your matplotlib figure and axes object ahead of time, and explicitly plot the dataframe on that:

from matplotlib import pyplot
import pandas
import statsmodels.api as sm

df = pandas.read_csv(...)

fig, ax = pyplot.subplots()
df.plot(x='xcol', y='ycol', ax=ax)

Then you still have that axes object around to use directly to plot your line:

model = sm.formula.ols(formula='ycol ~ xcol', data=df)
res = model.fit()
df.assign(fit=res.fittedvalues).plot(x='xcol', y='fit', ax=ax)