Fill missing values in the frame using the specified function. The specified function is called with all series and keys for which the frame does not contain value and the result of the call is used in place of the missing value. The operation is only applied to columns (series) that contain values of the same type as the return type of the provided filling function. The operation does not attempt to convert between numeric values (so a series containing `float` will not be converted to a series of `int`). ## Parameters - `frame` - An input data frame that is to be filled - `f` - A function that takes a series `Series<R, T>` together with a key `K` in the series and generates a value to be used in a place where the original series contains a missing value. [category:Missing values]

public static Frame<R, C> FillMissingUsing<R, T, C>(
	FSharpFunc<Series<R, T>, FSharpFunc<R, T>> f,
	Frame<R, C> frame
)