Matlab C Library Matrix Operations
| Table of Contents |
Matlab C Library Matrix Operations
#include <matrix.h>
Type/Structure
mwIndex (C and Fortran) Type for index values mwPointer (Fortran) Declare appropriate pointer type for platform mwSize (C and Fortran) Type for size values mxArray (C and Fortran) Type for a MATLAB array
Getters
mxGetCell (C and Fortran) Get contents of mxArray cell mxGetChars (C) Get pointer to character array data mxGetClassID (C and Fortran) Get class of mxArray mxGetClassName (C and Fortran) Get class of mxArray as string mxGetData (C and Fortran) Get pointer to data mxGetDimensions (C and Fortran) Get pointer to dimensions array mxGetElementSize (C and Fortran) Get number of bytes required to store each data element mxGetEps (C and Fortran) Get value of eps mxGetField (C and Fortran) Get field value, given field name and index into structure array mxGetFieldByNumber (C and Fortran) Get field value, given field number and index into structure array mxGetFieldNameByNumber (C and Fortran) Get field name, given field number in structure array mxGetFieldNumber (C and Fortran) Get field number, given field name in structure array mxGetImagData (C and Fortran) Get pointer to imaginary data of mxArray mxGetInf (C and Fortran) Get value of infinity mxGetIr (C and Fortran) Get ir array of sparse matrix mxGetJc (C and Fortran) Get jc array of sparse matrix mxGetLogicals (C) Get pointer to logical array data mxGetM (C and Fortran) Get number of rows in mxArray mxGetN (C and Fortran) Get number of columns in mxArray mxGetNaN (C and Fortran) Get value of NaN (Not-a-Number) mxGetNumberOfDimensions (C and Fortran) Get number of dimensions in mxArray mxGetNumberOfElements (C and Fortran) Get number of elements in mxArray mxGetNumberOfFields (C and Fortran) Get number of fields in structure mxArray mxGetNzmax (C and Fortran) Get number of elements in ir, pr, and pi arrays mxGetPi (C and Fortran) Get imaginary data elements in mxArray mxGetPr (C and Fortran) Get real data elements in mxArray mxGetProperty (C and Fortran) Get property value of MATLAB class object mxGetScalar (C and Fortran) Get real component of first data element in mxArray mxGetString (C and Fortran) Copy string mxArray to C-style string
Setters
mxSetCell (C and Fortran) Set value of one cell of mxArray mxSetClassName (C) Convert structure array to MATLAB object array mxSetData (C and Fortran) Set pointer to data mxSetDimensions (C and Fortran) Modify number of dimensions and size of each dimension mxSetField (C and Fortran) Set structure array field, given field name and index mxSetFieldByNumber (C and Fortran) Set structure array field, given field number and index mxSetImagData (C and Fortran) Set imaginary data pointer for mxArray mxSetIr (C and Fortran) Set ir array of sparse mxArray mxSetJc (C and Fortran) Set jc array of sparse mxArray mxSetM (C and Fortran) Set number of rows in mxArray mxSetN (C and Fortran) Set number of columns in mxArray mxSetNzmax (C and Fortran) Set storage space for nonzero elements mxSetPi (C and Fortran) Set new imaginary data for mxArray mxSetPr (C and Fortran) Set new real data for mxArray mxSetProperty (C and Fortran) Set value of property of MATLAB class object
Is
mxIsCell (C and Fortran) Determine whether input is cell mxArray mxIsChar (C and Fortran) Determine whether input is string mxArray mxIsClass (C and Fortran) Determine whether mxArray is member of specified class mxIsComplex (C and Fortran) Determine whether data is complex mxIsDouble (C and Fortran) Determine whether mxArray represents data as double-precision, floating-point numbers mxIsEmpty (C and Fortran) Determine whether mxArray is empty mxIsFinite (C and Fortran) Determine whether input is finite mxIsFromGlobalWS (C and Fortran) Determine whether mxArray was copied from MATLAB global workspace mxIsInf (C and Fortran) Determine whether input is infinite mxIsInt16 (C and Fortran) Determine whether mxArray represents data as signed 16-bit integers mxIsInt32 (C and Fortran) Determine whether mxArray represents data as signed 32-bit integers mxIsInt64 (C and Fortran) Determine whether mxArray represents data as signed 64-bit integers mxIsInt8 (C and Fortran) Determine whether mxArray represents data as signed 8-bit integers mxIsLogical (C and Fortran) Determine whether mxArray is of type mxLogical mxIsLogicalScalar (C) Determine whether scalar mxArray is of type mxLogical mxIsLogicalScalarTrue (C) Determine whether scalar mxArray of type mxLogical is true mxIsNaN (C and Fortran) Determine whether input is NaN (Not-a-Number) mxIsNumeric (C and Fortran) Determine whether mxArray is numeric mxIsSingle (C and Fortran) Determine whether mxArray represents data as single-precision, floating-point numbers mxIsSparse (C and Fortran) Determine whether input is sparse mxArray mxIsStruct (C and Fortran) Determine whether input is structure mxArray mxIsUint16 (C and Fortran) Determine whether mxArray represents data as unsigned 16-bit integers mxIsUint32 (C and Fortran) Determine whether mxArray represents data as unsigned 32-bit integers mxIsUint64 (C and Fortran) Determine whether mxArray represents data as unsigned 64-bit integers mxIsUint8 (C and Fortran) Determine whether mxArray represents data as unsigned 8-bit integers
Alloc/Free
mxCalloc (C and Fortran) Allocate dynamic memory for array using MATLAB memory manager mxCreateCellArray (C and Fortran) Create unpopulated N-D cell mxArray mxCreateCellMatrix (C and Fortran) Create unpopulated 2-D cell mxArray mxCreateCharArray (C and Fortran) Create unpopulated N-D string mxArray mxCreateCharMatrixFromStrings (C and Fortran) Create populated 2-D string mxArray mxCreateDoubleMatrix (C and Fortran) Create 2-D, double-precision, floating-point mxArray initialized to 0 mxCreateDoubleScalar (C and Fortran) Create scalar, double-precision array initialized to specified value mxCreateLogicalArray (C) Create N-D logical mxArray initialized to false mxCreateLogicalMatrix (C) Create 2-D, logical mxArray initialized to false mxCreateLogicalScalar (C) Create scalar, logical mxArray mxCreateNumericArray (C and Fortran) Create unpopulated N-D numeric mxArray mxCreateNumericMatrix (C and Fortran) Create numeric matrix and initialize data elements to 0 mxCreateSparse (C and Fortran) Create 2-D unpopulated sparse mxArray mxCreateSparseLogicalMatrix (C) Create unpopulated 2-D, sparse, logical mxArray mxCreateString (C and Fortran) Create 1-by-N string mxArray initialized to specified string mxCreateStructArray (C and Fortran) Create unpopulated N-D structure mxArray mxCreateStructMatrix (C and Fortran) Create unpopulated 2-D structure mxArray mxDestroyArray (C and Fortran) Free dynamic memory allocated by mxCreate* functions mxDuplicateArray (C and Fortran) Make deep copy of array mxFree (C and Fortran) Free dynamic memory allocated by mxCalloc, mxMalloc, or mxRealloc mxMalloc (C and Fortran) Allocate dynamic memory using MATLAB memory manager mxRealloc (C and Fortran) Reallocate memory mxRemoveField (C and Fortran) Remove field from structure array
Others
mxAddField (C and Fortran) Add field to structure array mxArrayToString (C) Convert array to string mxAssert (C) Check assertion value for debugging purposes mxAssertS (C) Check assertion value without printing assertion text mxCalcSingleSubscript (C and Fortran) Offset from first element to desired element mxChar (C) Type for string mxArray mxClassID (C) Enumerated value identifying class of mxArray mxComplexity (C) Flag specifying whether mxArray has imaginary components
Examples
Create a mxArray
double mat[] = {
11, 21,
12, 22,
13, 23,
14, 24
};
int nRow = 2; // M = 2;
int nCol = 4; // N = 4;
// Allocate memory. mxCOMPLEX for complex array
mxArray* X = mxCreateDoubleMatrix(nRow, nCol, mxREAL);
// Assign
memcpy(mxGetPr(X), mat, nRow*nCol*sizeof(double));
mxDestroyArray(X);
mxSetPr
// Prepare data
double mat[] = {
11, 21,
12, 22,
13, 23,
14, 24
};
// mxSetPr requires dynamic array mxCalloc/mxMalloc/mxRealloc
double* matmat = mxCalloc(nRow*nCol, sizeof(double));
memcpy(matmat, mat, nRow*nCol*sizeof(double));
mwSize nRow = 2; // M = 2;
mwSize nCol = 4; // N = 4;
mxArray* X = mxCreateDoubleMatrix(nRow, nCol, mxREAL);
// Free before mxSetPr because mxSetPr allocates new memory
mxFree(mxGetPr(X));
mxSetPr(X, matmat);
mxDestroyArray(X);
// mxCalloc/mxMalloc/mxRealloc are freed via mxFree
mxFree(matmat);
double mat[] = {
11, 21,
12, 22,
13, 23,
14, 24
};
// mxSetPr requires dynamic array mxCalloc/mxMalloc/mxRealloc
double* matmat = mxCalloc(nRow*nCol, sizeof(double));
memcpy(matmat, mat, nRow*nCol*sizeof(double));
mwSize nRow = 2; // M = 2;
mwSize nCol = 4; // N = 4;
// Do not allocate memory yet not to free as above
mxArray* X = mxCreateDoubleMatrix(0, 0, mxREAL);
mxSetM(nRow);
mxSetN(nCol);
mxSetPr(X, matmat);
mxDestroyArray(X);
mxFree(mat);
Access to mxArray
mwSize row, col; // mwSize is int
// When using the mex -largeArrayDims switch, mwSize is equivalent to size_t
mwSize nRow = mxGetM(xData);
mwSize nCol = mxGetN(xData);
double *xValues = mxGetPr(xData);
for(row = 0; row < nRow; row++) {
for(col = 0; col < nCol; col++) {
printf("%lf, *xValues[nRow * col + row]);
}
printf("\n");
}
Create a cell array
mwSize ndim = 1;
mwSize dims[] = {2};
mxArray* cell = mxCreateCellArray(ndim, dims);
mxArray* X1 = mxCreateDoubleMatrix(3, 4, mxREAL);
mxArray* X2 = mxCreateDoubleMatrix(1, 5, mxREAL);
mxSetCell(cell, (mxIndex)0, X1); // this allocates memory
mxSetCell(cell, (mxIndex)1, X2);
// destroy before re-set
mxDestroyArray(mxGetCell(cell, 0)); // does not free X1
mxDestroyArray(mxGetCell(cell, 1));
mxArray* Y1 = mxCreateDoubleMatrix(3, 4, mxREAL);
mxArray* Y2 = mxCreateDoubleMatrix(1, 5, mxREAL);
mxSetCell(cell, (mxIndex)0, Y1);
mxSetCell(cell, (mxIndex)1, Y2);
mxDestroyArray(X1);
mxDestroyArray(X2);
mxDestroyArray(Y1);
mxDestroyArray(Y2);
mxDestroyArray(cell);
Print a 3-D array
void cvmxPrintMatrix(const mxArray* mxarr)
{
int nDim;
const int *dims;
int row, col, z;
mxClassID classid;
classid = mxGetClassID(mxarr);
nDim = mxGetNumberOfDimensions(mxarr);
dims = mxGetDimensions(mxarr);
if (classid == mxUINT8_CLASS) {
unsigned char *mxData = mxGetData(mxarr);
for (z = 0; z < dims[2]; z++) {
for (row = 0; row < dims[0]; row++) {
for (col = 0; col < dims[1]; col++) {
printf("%d ", mxData[
dims[0] * dims[1] * z + dims[0] * col + row]);
}
printf("\n");
}
printf("\n");
}
} else if (classid == mxDOUBLE_CLASS) {
double *mxData = mxGetData(mxarr);
for (z = 0; z < dims[2]; z++) {
for (row = 0; row < dims[0]; row++) {
for (col = 0; col < dims[1]; col++) {
printf("%lf ", mxData[
dims[0] * dims[1] * z + dims[0] * col + row]);
}
printf("\n");
}
printf("\n");
}
} else if (classid == mxSINGLE_CLASS) {
float *mxData = mxGetData(mxarr);
for (z = 0; z < dims[2]; z++) {
for (row = 0; row < dims[0]; row++) {
for (col = 0; col < dims[1]; col++) {
printf("%lf ", mxData[
dims[0] * dims[1] * z + dims[0] * col + row]);
}
printf("\n");
}
printf("\n");
}
}
}
