"??? Undefined function or method" in Matlab Engine command window

Question

I am working with Visual Studio on C++ code, and I send some variables to MATLAB engine. So far there is no problem. Imagine I have the MATLAB command window opened and these variables:

» whos
  Name            Size             Bytes  Class     Attributes

  QWe             1x365             2920  double              
  QWp             1x364             2912  double              
  QWu             1x364             2912  double 

I can use the standard MATLAB functions, but I have dowloaded a new function.m (which works in MATLAB normally after setting the path) that this command window from MATLAB's engine is not recognizing or finding.

» isnormq(Q)
??? Undefined function or method 'isnormq'

I thought they (command window and MATLAB) were synchronized but now I see they aren't.

How can I solve this so I can use my function.m from the command window? Any help will be welcomed.

Answer 1

As it has been a long time and nobody answered I will post what I did:

In Matlab everytime you need a newtoolbox you link the path once and there stays "forever". You can use functions from the toolbox as if they were by default in Matlab.

Using matlab engine this doesn't work that way so it is necessary to write the command line:

% Here we load the toolbox for converting quaternion to Euler Angles
addpath(genpath('C:\Program Files (x86)\MATLAB\R2010a\toolbox\SpinCalc')); //for example

Answer 2

It's been a long time but I face the same problem and find some interesting information about it.

First of all at the newer version of MATLAB (2016a) MATLAB Engine search path is C:\Program Files\MATLAB\R2016a (Or the same path where you install MATLAB). So if you don't change it C++ can use all the build-in functions. Furthermore, you can using functions from Toolboxes!

But there is another one problem: what about user defined functions? So I need to put .m file directly to C:\Program Files\MATLAB\R2016a to make it visible for MATLAB Engine.

Here we can go another way - just add the path of your .m file to MATLAB through C++:

char CommandChangePath[MAX_PATH];
strcpy(CommandChangePath, "addpath('C:\\Users\\SuperUser\\Documents\\Visual Studio 2017\\Projects\\MyCppProject')");
engEvalString(ep, CommandChangePath);

For me its very useful to put necessary MATLAB function in current C++ project, add the path and use then! Now you don't need to change the path at every step - it's remembered and useful always for current application.