PortfolioMAD Object Properties and Functions
PortfolioMAD object implements mean absolute-deviation
(MAD) portfolio optimization and is derived from the abstract class
AbstractPortfolio. Every property and function of the
PortfolioMAD object is public, although some properties and
functions are hidden. The
PortfolioMAD object is a value object
where every instance of the object is a distinct version of the object. Since the
PortfolioMAD object is also a MATLAB® object, it inherits the default functions associated with MATLAB objects.
Working with PortfolioMAD Objects
PortfolioMAD object and its functions are an interface for mean
absolute-deviation portfolio optimization. So, almost everything you do with the
PortfolioMAD object can be done using the functions. The
basic workflow is:
Design your portfolio problem.
PortfolioMADto create the
PortfolioMADobject or use the various set functions to set up your portfolio problem.
Use estimate functions to solve your portfolio problem.
In addition, functions are available to help you view intermediate
results and to diagnose your computations. Since MATLAB features are part of a
PortfolioMAD object, you can
save and load objects from your workspace and create and manipulate arrays of
objects. After settling on a problem, which, in the case of MAD portfolio
optimization, means that you have either scenarios, data, or moments for asset
returns, and a collection of constraints on your portfolios, use
PortfolioMAD to set the properties
PortfolioMAD lets you create an object from scratch or update an
existing object. Since the
PortfolioMAD object is a value object,
it is easy to create a basic object, then use functions to build upon the basic
object to create new versions of the basic object. This is useful to compare a basic
problem with alternatives derived from the basic problem. For details, see Creating the PortfolioMAD Object.
Setting and Getting Properties
You can set properties of a
PortfolioMAD object using either
PortfolioMAD or various
Although you can also set properties directly, it is not recommended since error-checking is not performed when you set a property directly.
PortfolioMAD object supports setting
properties with name-value pair arguments such that each argument name is a property
and each value is the value to assign to that property. For example, to set the
Budget properties in an
p, use the
p = PortfolioMAD(p,'LowerBound', 0,'Budget',1);
In addition to the
PortfolioMAD object, which lets you
set individual properties one at a time, groups of properties are set in a
PortfolioMAD object with various “set” and
“add” functions. For example, to set up an average turnover
constraint, use the
setTurnover function to specify the
bound on portfolio turnover and the initial portfolio. To get individual properties
PortfolioMAD object, obtain properties directly or use an
assortment of “get” functions that obtain groups of properties from a
PortfolioMAD object. The
PortfolioMAD object and
set functions have several useful features:
setfunctions try to determine the dimensions of your problem with either explicit or implicit inputs.
setfunctions try to resolve ambiguities with default choices.
setfunctions perform scalar expansion on arrays when possible.
The PortfolioMAD functions try to diagnose and warn about problems.
Displaying PortfolioMAD Objects
PortfolioMAD object uses the default display function provided by
PortfolioMAD object and its properties with or without the
object variable name.
Saving and Loading PortfolioMAD Objects
Save and load
PortfolioMAD objects using the MATLAB
Estimating Efficient Portfolios and Frontiers
Estimating efficient portfolios and efficient frontiers is the primary purpose of the MAD portfolio optimization tools. An efficient portfolio are the portfolios that satisfy the criteria of minimum risk for a given level of return and maximum return for a given level of risk. A collection of “estimate” and “plot” functions provide ways to explore the efficient frontier. The “estimate” functions obtain either efficient portfolios or risk and return proxies to form efficient frontiers. At the portfolio level, a collection of functions estimates efficient portfolios on the efficient frontier with functions to obtain efficient portfolios:
At the endpoints of the efficient frontier
That attain targeted values for return proxies
That attain targeted values for risk proxies
Along the entire efficient frontier
These functions also provide purchases and sales needed to shift from an initial or current portfolio to each efficient portfolio. At the efficient frontier level, a collection of functions plot the efficient frontier and estimate either risk or return proxies for efficient portfolios on the efficient frontier. You can use the resultant efficient portfolios or risk and return proxies in subsequent analyses.
Arrays of PortfolioMAD Objects
Although all functions associated with a
PortfolioMAD object are designed
to work on a scalar
PortfolioMAD object, the array capabilities
of MATLAB enable you to set up and work with arrays of
PortfolioMAD objects. The easiest way to do this is with the
repmat function. For example, to
create a 3-by-2 array of
p = repmat(PortfolioMAD, 3, 2); disp(p)
3×2 PortfolioMAD array with properties: BuyCost SellCost RiskFreeRate Turnover BuyTurnover SellTurnover NumScenarios Name NumAssets AssetList InitPort AInequality bInequality AEquality bEquality LowerBound UpperBound LowerBudget UpperBudget GroupMatrix LowerGroup UpperGroup GroupA GroupB LowerRatio UpperRatio MinNumAssets MaxNumAssets BoundType
PortfolioMADobjects, you can work on individual
PortfolioMADobjects in the array by indexing. For example:
p(i,j) = PortfolioMAD(p(i,j), ... );
PortfolioMADfor the (
j) element of a matrix of
PortfolioMADobjects in the variable
If you set up an array of
PortfolioMAD objects, you can access properties
of a particular
PortfolioMAD object in the array by indexing so
that you can set the lower and upper bounds
ub for the
k) element of a
3-D array of
p(i,j,k) = setBounds(p(i,j,k),lb, ub);
[lb, ub] = getBounds(p(i,j,k));
PortfolioMADobject functions work on only one
PortfolioMADobject at a time.
Subclassing PortfolioMAD Objects
You can subclass the
PortfolioMAD object to override existing functions or
to add new properties or functions. To do so, create a derived class from the
PortfolioMAD class. This gives you all the properties and
functions of the
PortfolioMAD class along with any new features
that you choose to add to your subclassed object. The
PortfolioMAD class is derived from an abstract class called
AbstractPortfolio. Because of this, you can also create a
derived class from
AbstractPortfolio that implements an entirely
different form of portfolio optimization using properties and functions of the
Conventions for Representation of Data
The MAD portfolio optimization tools follow these conventions regarding the representation of different quantities associated with portfolio optimization:
Asset returns or prices for scenarios are in matrix form with samples for a given asset going down the rows and assets going across the columns. In the case of prices, the earliest dates must be at the top of the matrix, with increasing dates going down.
Portfolios are in vector or matrix form with weights for a given portfolio going down the rows and distinct portfolios going across the columns.
Constraints on portfolios are formed in such a way that a portfolio is a column vector.
Portfolio risks and returns are either scalars or column vectors (for multiple portfolio risks and returns).