Error using eval in matlabcontrol

Question

I used MatlabConrol to connect Java and MATLAB. I want to send an image path to MATLAB to process it with matching functions and give me back a number of similar images and paths, to show in the Java GUI.

I always get the same error when passing an image path to MATLAB:

Error using eval
Undefined function 'getinput' for input arguments of type 'char'.

Here's my MATLAB function:

function matlab = getinput(input)
results = hgr(input);

And my Java code:

imag = ImageIO.read(fileChoose.getSelectedFile());
ImagePath = fileChoose.getSelectedFile().getAbsolutePath();

public void SendingMatlabControl() throws MatlabConnectionException,
  MatlabInvocationException {
  // create proxy
  MatlabProxy proxy;
  // Create a proxy, which we will use to control MATLAB
  MatlabProxyFactory factory = new MatlabProxyFactory();
  proxy = factory.getProxy();
  // Display 'hello world' like before, but this time using feval
    try {
      // call builtin function
      proxy.eval("getinput('imagepath')");
      // call user-defined function (must be on the path)
      proxy.eval("addpath('E:\\vm')");
      proxy.feval("matlab");
      proxy.eval("rmpath('E:\\vm)");
    } catch (MatlabInvocationException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    // Disconnect the proxy from MatLab
    proxy.disconnect();
  }

Your comment 'call builtin function' seems to suggest that getinput is a builtin function, but I couldn't find any mention of it on the MathWorks website. Are you sure this is a builtin function? — Luke Woodward
– Luke Woodward, Commented Jul 1, 2012 at 8:09

Amro · Accepted Answer · 2012-07-01 08:36:12Z

3

Let me give an example of calling a function, passing it input, and retrieving the output. There are two ways, either:

use eval and assign the result of the function inside the MATLAB workspace, then retrieve those variables using getVariable, or
use returningFeval to evaluate the function with its inputs, and directly retrieve the output.

Suppose we had a MATLAB function myfunc.m that takes a string as input, and returns a cell array containing a string, a number, and a vector:

function out = myfunc(str)
    out = cell(3,1);
    out{1} = sprintf('Welcome to %s!', str);
    out{2} = 99;
    out{3} = rand(10,1);
end

Here is the Java code:

import matlabcontrol.*;

public class TestMyFunc
{
    public static void main(String[] args)
        throws MatlabConnectionException, MatlabInvocationException
    {
        // create proxy
         MatlabProxyFactoryOptions options =
            new MatlabProxyFactoryOptions.Builder()
                .setUsePreviouslyControlledSession(true).build();
        MatlabProxyFactory factory = new MatlabProxyFactory(options);
        MatlabProxy proxy = factory.getProxy();

        // call function and get output cell array
        String in = "Stack Overflow";
        Object[] out = proxy.returningFeval("myfunc", 1, in);

        // extract stuff from cell array
        out = (Object[]) out[0];
        String str = (String) out[0];
        double x = ((double[]) out[1])[0];
        double[] arr = (double[]) out[2];

        // show result
        System.out.println("str =\n " + str);
        System.out.println("x = \n " + x);
        System.out.println("arr =");
        for(int i=0; i < arr.length; i++) {
            System.out.println(" " + arr[i]);
        }

        // shutdown MATLAB
        //proxy.feval("quit");

        // close connection
        proxy.disconnect();
    }
}

I get the output:

str =
 Welcome to Stack Overflow!
x =
 99.0
arr =
 0.5974901918725793
 0.3353113307052461
 0.29922502333310663
 0.45259254156932405
 0.42264565322046244
 0.35960631797223563
 0.5583191998692971
 0.7425453657019391
 0.42433478362569066
 0.42935578857620504

answered Jul 1, 2012 at 8:36

Amro

125k25 gold badges250 silver badges466 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

user1318251 Over a year ago

okay that's all good but now i need to firstly pass image path using feval then when all m files will execute ,i will use returningFeval as u mentioned above to retrieve output number of image (tell me if i'm wrong ) ,,,problem i still have same exception ,do u see any problems in my code above ,i really losing my mind :(

Amro Over a year ago

@user1318251: no, you use returningFeval to call your m-function passing image path and retrieving result at the same time. Please read the project Wiki and Java docs

user1318251 Over a year ago

i run your code and still have this error "Undefined function 'myfunc' for input arguments of type 'char'." and when running your matlab function it gave me this error "Error using myfuncs (line 3) Not enough input arguments." do you know what's the problem ?

Amro Over a year ago

@user1318251: myfunc must be on the MATLAB path. It worked for me because matlabcontrol starts the MATLAB session in the same working directory that contains the function file myfunc.m. A more general solution would be to simply set up the path at the beginning: proxy.eval("addpath('c:\\path\to\folder')");)

user1318251 Over a year ago

so it would be better to change location of m files to same directory where i setup MATLAB which is C directory (that's what you are saying ?)?

|

Collectives™ on Stack Overflow

Error using eval in matlabcontrol

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related