apply.fromstart: calculate a function over an expanding window always starting from the beginning of the series
Description
A function to calculate a function over an expanding window from the start of the timeseries. This wrapper allows easy calculation of from inception statistics.
Usage
apply.fromstart(R, FUN = "mean" , gap = 1, ...)
Arguments
R
an xts, vector, matrix, data frame, timeSeries or zoo object of asset returns
FUN
any function that can be evaluated using a single set of returns (e.g., rolling beta won't work, but Return.annualized will)
gap
the number of data points from the beginning of the series required to train the calculation