def test_grid():
# Load Data
clrd = cl.load_dataset('clrd')
medmal_paid = clrd.groupby('LOB').sum().loc['medmal']['CumPaidLoss']
medmal_prem = clrd.groupby(
'LOB').sum().loc['medmal']['EarnedPremDIR'].latest_diagonal
medmal_prem.rename('development', ['premium'])
# Pipeline
dev = cl.Development()
tail = cl.TailCurve()
benk = cl.Benktander()
steps = [('dev', dev), ('tail', tail), ('benk', benk)]
pipe = cl.Pipeline(steps)
# Prep Benktander Grid Search with various assumptions, and a scoring function
param_grid = dict(benk__n_iters=[250], benk__apriori=[1.00])
scoring = {'IBNR': lambda x: x.named_steps.benk.ibnr_.sum()[0]}
grid = cl.GridSearch(pipe, param_grid, scoring=scoring)
# Perform Grid Search
grid.fit(medmal_paid, benk__sample_weight=medmal_prem)
assert grid.results_['IBNR'][0] == \
cl.Benktander(n_iters=250, apriori=1).fit(cl.TailCurve().fit_transform(cl.Development().fit_transform(medmal_paid)), sample_weight=medmal_prem).ibnr_.sum()[0]
def test_grid():
# Load Data
clrd = cl.load_sample("clrd")
medmal_paid = clrd.groupby("LOB").sum().loc["medmal"]["CumPaidLoss"]
medmal_prem = (clrd.groupby("LOB").sum().loc["medmal"]
["EarnedPremDIR"].latest_diagonal)
medmal_prem.rename("development", ["premium"])
# Pipeline
dev = cl.Development()
tail = cl.TailCurve()
benk = cl.Benktander()
steps = [("dev", dev), ("tail", tail), ("benk", benk)]
pipe = cl.Pipeline(steps)
# Prep Benktander Grid Search with various assumptions, and a scoring function
param_grid = dict(benk__n_iters=[250], benk__apriori=[1.00])
scoring = {"IBNR": lambda x: x.named_steps.benk.ibnr_.sum()}
grid = cl.GridSearch(pipe, param_grid, scoring=scoring)
# Perform Grid Search
grid.fit(medmal_paid, benk__sample_weight=medmal_prem)
assert (grid.results_["IBNR"][0] == cl.Benktander(
n_iters=250, apriori=1).fit(
cl.TailCurve().fit_transform(
cl.Development().fit_transform(medmal_paid)),
sample_weight=medmal_prem,
).ibnr_.sum())
and as ``n_iters`` approaches infinity yields the chainladder. As ``n_iters``
increases the apriori selection becomes less relevant regardless of initial
choice.
"""
import chainladder as cl
# Load Data
clrd = cl.load_sample('clrd')
medmal_paid = clrd.groupby('LOB').sum().loc['medmal', 'CumPaidLoss']
medmal_prem = clrd.groupby('LOB').sum().loc['medmal', 'EarnedPremDIR'].latest_diagonal
medmal_prem.rename('development', ['premium'])
# Generate LDFs and Tail Factor
medmal_paid = cl.Development().fit_transform(medmal_paid)
medmal_paid = cl.TailCurve().fit_transform(medmal_paid)
# Benktander Model
benk = cl.Benktander()
# Prep Benktander Grid Search with various assumptions, and a scoring function
param_grid = dict(n_iters=list(range(1,100,2)),
apriori=[0.50, 0.75, 1.00])
scoring = {'IBNR':lambda x: x.ibnr_.sum()}
grid = cl.GridSearch(benk, param_grid, scoring=scoring)
# Perform Grid Search
grid.fit(medmal_paid, sample_weight=medmal_prem)
# Plot data
grid.results_.pivot(index='n_iters', columns='apriori', values='IBNR').plot(
title='Benktander convergence to Chainladder', grid=True).set(ylabel='IBNR')
====================================================
Basic Assumption Tuning with Pipeline and Gridsearch
====================================================
This example demonstrates testing multiple number of periods in the development
transformer to see its influence on the overall ultimate estimate.
"""
import seaborn as sns
sns.set_style('whitegrid')
import chainladder as cl
tri = cl.load_dataset('abc')
# Set up Pipeline
steps = [('dev', cl.Development()), ('chainladder', cl.Chainladder())]
params = dict(dev__n_periods=[item for item in range(2, 11)])
pipe = cl.Pipeline(steps=steps)
# Develop scoring function that returns an Ultimate/Incurred Ratio
scoring = lambda x: x.named_steps.chainladder.ultimate_.sum(
) / tri.latest_diagonal.sum()
# Run GridSearch
grid = cl.GridSearch(pipe, params, scoring).fit(tri)
# Plot Results
grid.results_.plot(x='dev__n_periods', y='score',
marker='o').set(ylabel='Ultimate / Incurred')
we can see that the "Inverse Power" curve fit doesn't converge to its asymptotic
value.
"""
import chainladder as cl
tri = cl.load_sample('clrd').groupby('LOB').sum().loc['medmal', 'CumPaidLoss']
# Create a fuction to grab the scalar tail value.
def scoring(model):
""" Scoring functions must return a scalar """
return model.tail_.iloc[0, 0]
# Create a grid of scenarios
param_grid = dict(extrap_periods=list(range(1, 100, 6)),
curve=['inverse_power', 'exponential'])
# Fit Grid
model = cl.GridSearch(cl.TailCurve(), param_grid=param_grid,
scoring=scoring).fit(tri)
# Plot results
model.results_.pivot(
columns='curve', index='extrap_periods', values='score').plot(
grid=True,
ylim=(1, None),
title='Curve Fit Sensitivity to Extrapolation Period').set(
ylabel='Tail Factor')
traditional Bondy method.
"""
import chainladder as cl
# Fit basic development to a triangle
tri = cl.load_sample('tail_sample')['paid']
dev = cl.Development(average='simple').fit_transform(tri)
# Return both the tail factor and the Bondy exponent in the scoring function
scoring = {
'tail_factor': lambda x: x.tail_.values[0, 0],
'bondy_exponent': lambda x: x.b_.values[0, 0]
}
# Vary the 'earliest_age' assumption in GridSearch
param_grid = dict(earliest_age=list(range(12, 120, 12)))
grid = cl.GridSearch(cl.TailBondy(), param_grid, scoring)
results = grid.fit(dev).results_
ax = results.plot(x='earliest_age',
y='bondy_exponent',
title='Bondy Assumption Sensitivity',
marker='o')
results.plot(x='earliest_age',
y='tail_factor',
grid=True,
secondary_y=True,
ax=ax,
marker='o')
