Description Usage Arguments Details Value Author(s) References See Also Examples
This function generates a vector of investment weights for a long short portfolio where the the gross notional exposure is x.t.long + x.t.short and the net notional exposure is x.t.long - x.t.short. There are k non-zero positions in the portfolio.
1 2 | random.longshort(n = 2, k = n, segments = NULL, x.t.long = 1, x.t.short = x.t.long,
max.iter = 2000, eps = 0.001)
|
n |
A positive integer value for the number of investments in the portfolio |
k |
A positive integer value for the number of non zero weights |
segments |
A vector or list of vectors that defines the portfolio segments |
x.t.long |
A positive real value for the sum of the long exposures |
x.t.short |
A positive real value for the sum of the absolute value of the short exposures |
max.iter |
A positive integer value for the maximum iterations in the acceptance rejection method |
eps |
A small positive real value for the convergence criteria for the gross notional exposure |
The function implements an algorithm in which the outer structure is the iterative
acceptance rejection method. Within each iteration, the R function random.longonly
is used to construct a long only investment weight vector x.long
where the sum of
these weights is x.t.long
. The R function random.shortonly
is used to construct
a short only investment eight vector random.short
such that the sum of the absolute
value of these weights is x.t.long
. The sum of these two weight vectors, x.longshort
,
satisfies the net notional requirement of the desired portfolio. If the absolute value of
computed gross notiona exposure for x.longshort
minus $x.t.long + x.t.short$ is less than
the argument eps
, then the desired portfolio is generated and result is returned.
Otherwise, the process is repeated within the acceptance rejection loop until (1) the required
portfolio is generated or 2 the iteration limit is exceeded.
An n \times 1 vector of investment weights for the long short portfolio.
Frederick Novomestky fn334@nyu.edu
Jacobs, B. I. and K. N. Levy, 1997. The Long and Short of Long-Short Investing, Journal of Investing, Spring 1997, 73-86.
Jacobs, B. I., K. N. Levy and H. M. Markowitz, 2005. Portfolio Optimization with Factors, Scenarios and Realist SHort Positions, Operations Research, July/August 2005, 586-599.
random.longonly
,
random.shortonly
1 2 3 4 5 6 7 8 | ###
### long short portfolio of 30 investments with 30 non-zero positions
###
x <- random.longshort( 30 )
###
### long short portfolio of 30 investments with 10 non-zero positions
###
y <- random.longshort( 30, 10 )
|
Loading required package: truncdist
Loading required package: stats4
Loading required package: evd
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