Description Usage Arguments Details Author(s) References See Also Examples
The single factor model or CAPM Beta is the beta of an asset to the variance and covariance of an initial portfolio. Used to determine diversification potential.
1 2 3 4 5 6 7 | CAPM.beta(Ra, Rb, Rf = 0)
CAPM.beta.bull(Ra, Rb, Rf = 0)
CAPM.beta.bear(Ra, Rb, Rf = 0)
TimingRatio(Ra, Rb, Rf = 0)
|
Ra |
an xts, vector, matrix, data frame, timeSeries or zoo object of asset returns |
Rb |
return vector of the benchmark asset |
Rf |
risk free rate, in same period as your returns |
This function uses a linear intercept model to achieve the same results as
the symbolic model used by BetaCoVariance
beta = cov(Ra,Rb)/var(R)
Ruppert(2004) reports that this equation will give the estimated slope of the linear regression of Ra on Rb and that this slope can be used to determine the risk premium or excess expected return (see Eq. 7.9 and 7.10, p. 230-231).
Two other functions apply the same notion of best fit to positive and
negative market returns, separately. The CAPM.beta.bull
is a
regression for only positive market returns, which can be used to understand
the behavior of the asset or portfolio in positive or 'bull' markets.
Alternatively, CAPM.beta.bear
provides the calculation on negative
market returns.
The TimingRatio
may help assess whether the manager is a good timer
of asset allocation decisions. The ratio, which is calculated as
Timing Ratio = beta+/beta-
is best when greater than one in a rising market and less than one in a falling market.
While the classical CAPM has been almost completely discredited by the literature, it is an example of a simple single factor model, comparing an asset to any arbitrary benchmark.
Peter Carl
Sharpe, W.F. Capital Asset Prices: A theory of market
equilibrium under conditions of risk. Journal of finance, vol 19,
1964, 425-442.
Ruppert, David. Statistics and Finance, an
Introduction. Springer. 2004.
Bacon, Carl. Practical portfolio
performance measurement and attribution. Wiley. 2004.
BetaCoVariance
CAPM.alpha
CAPM.utils
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