Can't convert the Array to this TypedArray

Hi the mathworks community,

I have a quiet anoying problem with matlab C++ engine more precisely the matlab::data::TypedArray. I have wrote my C++ and matlab codes and compiled them successfully But I run the executable I got this:

terminate called after throwing an instance of 'matlab::data::detail::ArrayException<matlab::Exception, (matlab::data::ExceptionType)9>'

what(): Can't convert the Array to this TypedArray

Aborted (core dumped)

~I think that it occurs at the first line where I use matlab::data::TypedArray dataType:~

matlab::data::TypedArray<double> weedUV = factory.createArray<double>(
        { 1, 2 }, { 117.0, 91.0 });

And I found that pretty weird since I saw tons of example using exactly the same line. I URGENTLY NEED HELP GUYS!

Here is the entire C++ code:

#include "MatlabDataArray.hpp"
#include "MatlabEngine.hpp"
#include <iostream>

void client(matlab::engine::MATLABEngine* matlabPtr) {
    // Create MATLAB data array factory
    matlab::data::ArrayFactory factory;

    // Define the input arguments
    matlab::data::TypedArray<double> weedUV = factory.createArray<double>(
        { 1, 2 }, { 117.0, 91.0 }); //weedUV[0], weedUV[1]

    matlab::data::TypedArray<double> orientation = factory.createArray<double>(
        { 1, 4 }, { 0.1445, 0.784, 0.712, 0.456 }); //orientation.w, orientation.x, orientation.y, orientation.z 

    matlab::data::TypedArray<double> robotPosition = factory.createArray<double>(
        { 1, 2 }, { 5.947123, 2.1457 }); // robotPosition[0], robotPosition[1]

    matlab::data::CharArray cameraFrame = factory.createScalar("right_camera");
    
    //Define the projection Matrix
    matlab::data::TypedArray<double> const projectionMatrix = factory.createArray<double>(
        { 3, 4 }, {
        245.6983, 0.0, 318.6139, 0.0,
        0.0, 253.3011, 243.9297, 0.0,
        0.0, 0.0, 1.0, 0.0
        });
    
    // Pass vector containing 2 scalar args in vector    
    std::vector<matlab::data::Array> args({
        weedUV,
        orientation,
        robotPosition,
        projectionMatrix,
        cameraFrame});

    // Call the MATLAB function
    std::cout << "calling the api function" << std::endl;
    matlab::data::TypedArray<double> points = matlabPtr->feval(u"api", args);

    double x = points[0];
    double y = points[1];
    // Display results
    std::cout << "x: " << x << ", y: " << y << std::endl;
}

int main() {
    using namespace matlab::engine;
    // Start MATLAB engine synchronously
    std::unique_ptr<matlab::engine::MATLABEngine> matlabPtr = matlab::engine::startMATLAB();

    matlabPtr->eval(u"rosshutdown;");
    matlabPtr->eval(u"rosinit;");
    // Call the client function with the MATLAB engine pointer
    client(matlabPtr.get());
    matlabPtr->eval(u"rosshutdown;");
    return 0;
}

Answer 1

[Sanogo]

After a long debugging time, I noticed that the error was finally at this line:

matlab::data::CharArray cameraFrame = factory.createScalar("right_camera");

I thought this was the good way to create a matlab string through the C++ engine cause in matlab string != CharArray. But it looks like this doesn't impact my function so this worked:

matlab::data::CharArray cameraFrame = factory.createCharArray("right_camera");

Answer 2

[Ayush Kashyap]

Hi Sanogo,

Seeing the line of code, I believe it can be an issue of datatype of size.

You may try as following:

std::vector<size_t> size = {1, 2};
std::vector<double> data = {117.0, 91.0};
matlab::data::TypedArray<double> weedUV = factory.createArray<double>(size, data ...);

Using size_t datatype for defining size should resolve the error.

If the problem still persists, do check if appropriate libraries are lined properly or not, especially the one necessary for MATLAB Engine.

[Sanogo]

Thank you for the help @Ayush Kashyap!