How to marshal to MATLAB COM Interop

Hello,

I'm pretty sure I am seeing a marshaling issue interfacing with MATLAB. I've got a client wiring up just fine in a C# program, and want to call fft, I gather through the Feval call.

Question (or questions) is (are), how to specify and/or marshal the requisite inputs and outputs in such a way that we get the desired response.

There' a follow on call in many of the fft examples to linspace, but I gather that technically this is optional, unless we want to wire up for visualization or otherwise.

I've verified on the "simple" hello world scenario, I call Feval to "version" and obtain the desired response. Now I want to step it up a notch for fft, and so on.

Next from that, various bandpass filters.

I should also mention, we're running against R2011b.

Thank you.

Answer 1

[Michael]

Working through the examples via COM Interop, I am able to make a similar call to the "linspace".

matlab.Feval(@"linspace", 1, out lso, 0d, 1d, nfft / 2 + 1);

And with a bit of C# extension method and lambda persuasion, extract out the desired result.

So at this point I am thinking it's something in how arrays are being passed into MATLAB.

Am I in the ball park if I assume (which I am loathe to do) that it prefers arrays to be 2-dimensional, even if we're talking about a "single dimension" of sampled data? So in other words, instead of double[] (C#), I should be transforming that into double[,]?

Thank you...

[Michael]

That did the trick. Deal with "arrays" (loosely speaking) as terms of two dimensional arrays. Trick is to get the row/column-major gymnastics correct.

Answer 2

[Michael]

I am receiving the following exception:

System.Reflection.TargetInvocationException occurred HResult=-2146232828 Message=Exception has been thrown by the target of an invocation. Source=mscorlib StackTrace: at System.RuntimeType.InvokeDispMethod(String name, BindingFlags invokeAttr, Object target, Object[] args, Boolean[] byrefModifiers, Int32 culture, String[] namedParameters) at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams) InnerException: System.Runtime.InteropServices.COMException HResult=-2147467259 Message=Undefined function 'fft' for input arguments of type 'int32'. Source=Matlab.MLApp ErrorCode=-2147467259 InnerException:

And the call is something like this:

object temp; matlab.Feval(@"fft", 1, out temp, y, y.Length, nfft);

where y is the signal generated sample double[] (C# language level), and nfft is the next power of two length.

Answer 3

[Michael]

I have also verified "which fft" over the COM client connection, and received the valid response: "built-in (C:\\Program Files\\MATLAB\\R2011b\\toolbox\\matlab\\datafun\\@logical\\fft)". So it's not because fft could not be identified. It's got something to do with language-level expected params, COM Interop marshaling, something like that I think.