MATLAB® sparse arrays provide efficient storage of double or logical data that has a large percentage of zeros. MATLAB sparse arrays support arithmetic, logical, and indexing operations. For more information, see Sparse Matrices.
Use matlab::data::ArrayFactory
to create a matlab::data::SparseArray
array. Write the data for the sparse array into buffers and use these buffers to create the sparse array. Pass the sparse array to MATLAB using MATLABEngine::setVariable
.
#include "MatlabDataArray.hpp" #include "MatlabEngine.hpp" void sparseArray() { using namespace matlab::engine; // Connect to named shared MATLAB session started as: // matlab -r "matlab.engine.shareEngine('myMatlabEngine')" String session(u"myMatlabEngine"); std::unique_ptr<MATLABEngine> matlabPtr = connectMATLAB(session); // Define the data for the sparse array std::vector<double> data = { 3.5, 12.98, 21.76 }; std::vector<size_t> rows = { 0,0,1 }; std::vector<size_t> cols = { 0, 4, 8 }; size_t nnz = 3; // Create buffers for the data matlab::data::ArrayFactory factory; buffer_ptr_t<double> data_p = factory.createBuffer<double>(nnz); buffer_ptr_t<size_t> rows_p = factory.createBuffer<size_t>(nnz); buffer_ptr_t<size_t> cols_p = factory.createBuffer<size_t>(nnz); // Write data into the buffers double* dataPtr = data_p.get(); size_t* rowsPtr = rows_p.get(); size_t* colsPtr = cols_p.get(); std::for_each(data.begin(), data.end(), [&](const double& e) { *(dataPtr++) = e; }); std::for_each(rows.begin(), rows.end(), [&](const size_t& e) { *(rowsPtr++) = e; }); std::for_each(cols.begin(), cols.end(), [&](const size_t& e) { *(colsPtr++) = e; }); // Use the buffers to create the sparse array matlab::data::SparseArray<double> arr = factory.createSparseArray<double>({ 2,9 }, nnz, std::move(data_p), std::move(rows_p), std::move(cols_p)); // Put the sparse array in the MATLAB workspace matlabPtr->setVariable(u"s", arr); }
The MATLAB
whos
command shows that the array passed to the MATLAB workspace is a sparse array.
>> whos Name Size Bytes Class Attributes s 2x9 128 double sparse
For information on how to setup and build C++ engine programs, see Build C++ Engine Programs.
matlab::data::ArrayFactory
| matlab::engine::connectMATLAB
| matlab::engine::MATLABEngine