Method to convert wide to long format triangle

[xne0n]

Hello,
How do you guys convert your wide triangle (imported from, let's say, an excel file to a pandas dataframe) into the tabular long format required ?
I've looked up on the documentation and I don't find anything...
Thank you !

[jbogaardt]

Hi @xne0n ,

Thanks for the question. It's not documented. We should probably mention something in the docs or figure out how to support wide. I'd use pandas.unstack to get there. Something like this:

import chainladder as cl

# Suppose you have a wide triangle (perhaps copied from Excel clipboard...)
df = cl.load_sample('raa').to_frame()

# You can use pandas unstack to make wide format long
df = df.unstack().dropna().reset_index()
# make sure you have good column labels
df.columns = ['age', 'origin', 'values']
# and make a date-like valuation
df['valuation'] = (df['origin'].dt.year + df['age'] / 12 - 1).astype(int)
# Finally make a Triangle
cl.Triangle(df, origin='origin', development='valuation', columns='values')

[xne0n]

Thank you !