docs: update docstring for Portfolio.dcf.wealth_index

Author: chilango74

okama/portfolios/dcf.py

@@ -156,20 +156,30 @@ def set_mc_parameters(
 
     def wealth_index(self, discounting: Literal["fv", "pv"], include_negative_values: bool = False) -> pd.DataFrame:
         """
-        Wealth index Future Values (FV) time series for the portfolio with cash flow (contributions and
-        withdrawals).
+        Calculate wealth index time series for the portfolio with cash flow (contributions and withdrawals).
 
         Wealth index (Cumulative Wealth Index) is a time series that presents the value of portfolio over
         historical time period considering cash flows.
 
         Accumulated inflation time series is added if `inflation=True` in the Portfolio.
 
-        If there is no cash flow, Wealth index is obtained from the accumulated return multiplicated
+        If there is no cash flow, Wealth index is obtained from the accumulated return multiplied
         by the initial investments. That is: initial_amount_pv * (Acc_Return + 1)
 
+        Parameters
+        ----------
+        discounting : {'fv', 'pv'}
+            Type of discounting to apply:
+            - 'fv': Future Values - nominal values without discounting
+            - 'pv': Present Values - values discounted to present using the discount rate
+        include_negative_values : bool, default False
+            Whether to include negative wealth index values in the result.
+            If False, negative values are replaced with zeros.
+
         Returns
         -------
-            Time series of wealth index values for portfolio and accumulated inflation.
+        pd.DataFrame
+            Time series of wealth index values for portfolio and accumulated inflation (if applicable).
 
         Examples
         --------
@@ -178,7 +188,7 @@ def wealth_index(self, discounting: Literal["fv", "pv"], include_negative_values
         >>> ind = ok.IndexationStrategy(pf)  # Set Cash Flow Strategy parameters
         >>> ind.initial_investment = 100  # initial investments value
         >>> ind.frequency = "year"  # withdrawals frequency
-        >>> ind.amount = -0.5 * 12  # initial withdrawals amount
+        >>> ind.amount = -6  # initial withdrawals amount
         >>> ind.indexation = "inflation"  # the indexation is equal to inflation
         >>> pf.dcf.cashflow_parameters = ind  # assign the strategy to Portfolio
         >>> pf.dcf.wealth_index(discounting="fv", include_negative_values=False).plot()