Feval (External Interfaces Reference)

Evaluate MATLAB function in server

Syntax

MATLAB Client

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

Method Signatures

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

Visual Basic Client

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

Description

Feval executes the MATLAB function specified by the string functionname in the Automation server attached to handle h.

Indicate the number of outputs to be 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. There are four ways to pass an argument to the function being evaluated.

Passing Mechanism
Description

Pass the value itself

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

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

Pass a client variable

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

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

Reference a server variable

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

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

Note that the server variable is not reassigned.

Passing Mechanism	Description
Pass the value itself	To pass any numeric or string value, specify the value in the `Feval` argument list: a = h.Feval('sin', 1, -pi:0.01:pi);
Pass a client variable	To pass an argument that is assigned to a variable in the client, specify the variable name alone: x = -pi:0.01:pi; a = h.Feval('sin', 1, x);
Reference a server variable	To reference a variable that is defined in the server, specify the variable name followed by an equals (`=`) sign: h.PutWorkspaceData('x', 'base', -pi:0.01:pi); a = h.Feval('sin', 1, 'x='); Note that the server variable is not reassigned.

Remarks

If you want output from Feval to be displayed at the client window, you must assign a returned value.

Server function names, like Feval, are case sensitive when using the first two syntaxes shown in the Syntax section.

There is no difference in the operation of the three syntaxes shown above for the MATLAB client.

Examples

Passing Arguments -- MATLAB Client

This section contains a number of examples showing how to use Feval to execute MATLAB commands on a MATLAB Automation server.

Concatenate two strings in the server by passing the input strings in a call to strcat through Feval (strcat deletes trailing spaces; use leading spaces):

a = h.Feval('strcat', 1, 'hello', ' world')
a =
    'hello world'

Perform the same concatenation, passing a string and a local variable clistr that contains the second string:

clistr = ' world';
a = h.Feval('strcat', 1, 'hello', clistr)
a =
    'hello world'

This next example is different in that the variable srvstr is defined in the server, not the client. Putting an equals sign after a variable name (e.g., srvstr=) indicates that it a server variable, and that MATLAB should not expect the variable to be defined on the client:

% Define the variable srvstr on the server.
h.PutCharArray('srvstr', 'base', ' world')

% Pass the name of the server variable using 'name=' syntax
a = h.Feval('strcat', 1, 'hello', 'srvstr=')
a =
    'hello world'

Visual Basic Client

Here are the same examples shown above, but written for a Visual Basic client. These examples return the same strings as shown above.

Pass the two strings to the MATLAB function strcat on the server:

Dim Matlab As Object
Dim out As Object
Matlab = CreateObject("matlab.application")
out = Matlab.Feval("strcat", 1, "hello", " world")

Define clistr locally and pass this variable:

Dim clistr As String
clistr = " world"
out = Matlab.Feval("strcat", 1, "hello", clistr)

Pass the name of a variable defined on the server:

Matlab.PutCharArray("srvstr", "base", " world")
out = Matlab.Feval("strcat", 1, "hello", "srvstr=")

Feval Return Values -- MATLAB Client

Feval returns data from the evaluated function in a cell array. The cell array has one row for every return value. You can control how many values are returned using the second input argument to Feval, as shown in this example.

The second argument in the following example specifies that Feval return three outputs from the fileparts function. As is the case here, you can request fewer than the maximum number of return values for a function (fileparts can return up to four):

a = h.Feval('fileparts', 3, 'd:\work\ConsoleApp.cpp')
a =
    'd:\work'
    'ConsoleApp'
    '.cpp'

Convert the returned values from the cell array a to char arrays:

a{:}
ans =
d:\work

ans =
ConsoleApp

ans =
.cpp

Feval Return Values -- Visual Basic Client

Here is the same example, but coded in Visual Basic. Define the argument returned by Feval as an Object.

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

Execute GetCharArray