MatlabFunction

General Mission Analysis Tool

MatlabFunction

MatlabFunction — Declaration of an external MATLAB function

Description

The MatlabFunction resource declares to GMAT that the name given refers to an existing external function in the MATLAB language. This function can be called in the Mission Sequence like a built-in function, with some limitations. See the CallMatlabFunction reference for details. Both user-created functions and built-in functions (like cos or path) are supported.

GMAT supports passing data to and from MATLAB through the function. It requires that a supported and properly configured version of MATLAB exist on the system. See the MATLAB Interface documentation for general details on the interface.

Fields

Field Description

FunctionPath

Paths to add to the MATLAB search path when the associated function is called. Separate multiple paths with semicolons (on Windows) or colons (on other platforms).

Data Type	String
Allowed Values	Valid file path(s)
Access	set, get
Default Value	`MATLAB_FUNCTION_PATH` properties in the startup file
Units	N/A
Interfaces	GUI, script

GUI

The MatlabFunction GUI window is very simple; it has a single file input box for the function path, and a Browse button that lets you graphically select the path.

Remarks

Search Path

When a function declared as a MatlabFunction is called, GMAT starts MATLAB in the background with a custom, configurable search path. MATLAB then searches for the named function in this search path. The search is case-sensitive, so the name of the function name and the MatlabFunction resource must be identical.

The search path consists of the following components, in order:

FunctionPath field of the associated MatlabFunction resource (default: empty)
MATLAB_FUNCTION_PATH entries in the GMAT startup file (default: GMAT\userfunctions\matlab)

MATLAB search path (returned by the MATLAB path() function)

If multiple MATLAB functions are called within a run, the FunctionPath fields for each are prepended to the search path at the time of the function call.

Multiple paths can be combined in the FunctionPath field by separating the paths with a semicolon (on Windows) or a colon (on Mac OS X and Linux).

Working Directory

When MATLAB starts in the background, its working directory is set to the GMAT bin directory.

Examples

Call a simple built-in MATLAB function:

Create MatlabFunction sinh Create Variable x y BeginMissionSequence x = 1 [y] = sinh(x)

Call an external custom MATLAB function:

Create Spacecraft aSat Create ImpulsiveBurn aBurn Create Propagator aProp Create MatlabFunction CalcHohmann CalcHohmann.FunctionPath = 'C:\path\to\functions' Create Variable a_target mu dv1 dv2 mu = 398600.4415 BeginMissionSequence % calculate burns for circular Hohmann transfer (example) [dv1, dv2] = CalcHohmann(aSat.SMA, a_target, mu) % perform first maneuver aBurn.Element1 = dv1 Maneuver aBurn(aSat) % propagate to apoapsis Propagate aProp(aSat) {aSat.Apoapsis} % perform second burn aBurn.Element1 = dv2 Maneuver aBurn(aSat)

Return the MATLAB search path and working directory:

Create MatlabFunction path pwd Create String pathStr pwdStr Create ReportFile aReport BeginMissionSequence [pathStr] = path [pwdStr] = pwd Report aReport pathStr Report aReport pwdStr

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