augment_roc

augment_roc(
    data,
    date_column,
    close_column,
    periods=1,
    start_index=0,
    reduce_memory=False,
    engine='auto',
)

Add rate-of-change (ROC) columns to a pandas or polars DataFrame.

Parameters

Name	Type	Description	Default
data	DataFrame or GroupBy(pandas or polars)	Input financial data. Grouped inputs are expanded per group before computing ROC features.	required
date_column	str	Name of the column containing date information. Used to preserve the original ordering.	required
close_column	str	Name of the column containing closing prices on which the ROC is computed.	required
periods	int, tuple, or list	Lookback windows used for the denominator term. An integer adds a single ROC column, a tuple `(start, end)` expands to the inclusive range `start..end`, and a list provides explicit periods. Defaults to `1`.	`1`
start_index	int	Offset applied to the numerator. When `0` (default) the current value is used; otherwise the numerator uses `close.shift(start_index)`.	`0`
reduce_memory	bool	Attempt to reduce memory usage when operating on pandas data. If used with polars inputs a warning is emitted and no conversion is performed.	`False`
engine	(auto, pandas, polars)	Execution engine. `"auto"` (default) infers the backend from the input data type while also accepting explicit overrides.	`"auto"`

Returns

Name	Type	Description
	DataFrame	DataFrame with ROC columns appended. The return type matches the input backend (pandas or polars).

Notes

Rate of change is defined as ::

ROC = (Value_t - Value_{t-period}) / Value_{t-period}

When start_index is non-zero the numerator is taken from Value_{t-start_index} instead of the current value. The implementation safeguards against division by zero by returning NaN whenever the denominator is zero.

Examples

import polars as pl
import pytimetk as tk


df = tk.load_dataset("stocks_daily", parse_dates=["date"])

# Pandas DataFrame input (engine inferred)
roc_df = df.groupby("symbol").augment_roc(
    date_column="date",
    close_column="close",
    periods=[22, 63],
    start_index=5,
)

# Polars DataFrame input using the tk accessor
roc_pl = (
    pl.from_pandas(df.query("symbol == 'AAPL'"))
    .tk.augment_roc(
        date_column="date",
        close_column="close",
        periods=(5, 10),
    )
)