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Feval (COM)

Execute MATLAB function in Automation server

Synopsis

IDL Method Signature

HRESULT Feval([in] BSTR functionname, [in] long nargout, 
[out] VARIANT* result, [in, optional] VARIANT arg1, arg2, ...)

Microsoft Visual Basic Client

Feval(String functionname, long numout, 
arg1, arg2, ...) As Object

MATLAB Client

result = Feval(h,'functionName',numout,arg1,arg2,...)

Description

result = Feval(h,'functionName',numout,arg1,arg2,...) executes MATLAB® function functionName in the Automation server attached to h. The function name is case-sensitive. If functionName does not have input arguments, consider calling Execute instead.

COM functions are available on Microsoft® Windows® systems only.

Indicate the number of outputs returned by the function in a 1-by-1 double array, numout. The server returns output from the function in the cell array, result.

You can specify as many as 32 input arguments to be passed to the function. These arguments follow numout in the Feval argument list. The following table shows ways to pass an argument.

Passing Mechanism

Description

Pass the value itself

To pass any numeric or character value, specify the value in the Feval argument list:

a = Feval(h,'sin',1,-pi:0.01:pi);

Pass a client variable

To pass an argument assigned to a variable in the client, specify the variable name alone:

x = -pi:0.01:pi;
a = Feval(h,'sin',1,x);

Reference a server variable

To reference a variable defined in the server, specify the variable name followed by an equals (=) sign:

PutWorkspaceData(h,'x','base',-pi:0.01:pi);
a = Feval(h,'sin',1,'x=');

MATLAB does not reassign the server variable.

Examples

collapse all

This example shows how to pass string arguments to the MATLAB strcat command using Feval.

Create a Visual Basic .NET application with the following code.

type fevalPassingArguments.vb
Dim Matlab As Object 
Dim out As Object 
out = Nothing 
Matlab = CreateObject("matlab.application") 
Matlab.Feval("strcat",1,out,"hello"," world") 
Dim clistr As String
clistr = " world"
Matlab.Feval("strcat",1,out,"hello",clistr)
Matlab.PutCharArray("srvstr","base"," world")
Matlab.Feval("strcat",1,out,"hello","srvstr=")

This example shows how to return the filepath, name, and ext arguments from the fileparts function.

Feval returns data from the evaluated function in a cell array. The cell array has one row for every return value. You control the number of return values using the Feval numout argument.

Create a Visual Basic .NET client with the following code.

type fevalDefiningFevalReturnValues.vb
Dim Matlab As Object
Dim out As Object
Matlab = CreateObject("matlab.application")
Matlab.Feval("fileparts",3,out,"d:\work\ConsoleApp.cpp")

This example shows how to return a modified server variable.

Create a matrix, A, in the server.

Reshape A.MATLAB interprets A in the expression 'A=' as a server variable name.

The reshape function does not modify variable A. A is unchanged.

To get the result of the reshape function, use the numout argument to assign the value to C.

Create a Visual Basic .NET application with the following code.

type fevalModifiedServerVariables.vb
Dim Matlab As Object 
Dim rows As Double 
Dim cols As Double 
Dim out As Object 
out = Nothing 
Dim data(7) As Double 
For i = 0 To 7 
    data(i) = i * 15 
Next i 
Matlab = CreateObject("matlab.application") 
Matlab.PutWorkspaceData("A", "base", data) 
rows = 4 
cols = 2 
Matlab.Feval("reshape", 1, out, "A=", rows, cols)

Tips

  • To display the output from Feval in the client window, assign a return value.

Introduced before R2006a