Pointer to field value from structure array, given index and field number
#include "matrix.h" mxArray *mxGetFieldByNumber(const mxArray *pm, mwIndex index, int fieldnumber);
#include "fintrf.h" mwPointer mxGetFieldByNumber(pm, index, fieldnumber) mwPointer pm mwIndex index integer*4 fieldnumber
pmPointer to a structure mxArray
indexIndex of the desired element.
In C,
the first element of an mxArray has an index of 0.
The index of the last element is N-1,
where N is the number of elements in the array.
In Fortran, the first element of an mxArray has
an index of 1. The index of
the last element is N, where N is
the number of elements in the array.
See mxCalcSingleSubscript for more details on
calculating an index.
fieldnumberPosition of the field whose value you want to extract
In C, the first field within each element has a field number of
0, the second field has a field number of
1, and so on. The last field has a field number of
N-1, where N is the number of
fields.
In Fortran, the first field within each element has a field number of
1, the second field has a field number of
2, and so on. The last field has a field number of
N, where N is the number of
fields.
Pointer to the mxArray in the specified field for the desired
element, on success. Returns NULL in C (0 in
Fortran) if passed an invalid argument or if there is no value assigned to the specified
field. Common causes of failure include:
Specifying an array pointer pm that does not point to a
structure mxArray. Call mxIsStruct to determine whether
pm points to a structure
mxArray.
Specifying an index to an element outside the bounds of the
mxArray. For example, given a structure
mxArray that contains 10 elements, you cannot specify an
index greater than 9 in C
(10 in Fortran).
Specifying a nonexistent field number. Call
mxGetFieldNumber to determine the field number that
corresponds to a given field name.
Call mxGetFieldByNumber to get the value held in the specified
fieldnumber at the indexed element.
Do not call mxDestroyArray on an mxArray
returned by the mxGetFieldByNumber function.
Inputs to a MEX-file are constant read-only mxArrays.
Do not modify the inputs. Using mxSetCell* or mxSetField* functions
to modify the cells or fields of a MATLAB® argument causes unpredictable
results.
In C, if you have a 1-by-1 structure, then
calling:
mxGetField(pa, index, "field_name");
is equivalent to calling:
field_num = mxGetFieldNumber(pa, "field_name"); mxGetFieldByNumber(pa, index, field_num);
where index is 0.
In Fortran, if you have a 1-by-1 structure, then
calling:
mxGetField(pm, index, 'fieldname')
is equivalent to calling:
fieldnum = mxGetFieldNumber(pm, 'fieldname') mxGetFieldByNumber(pm, index, fieldnum)
where index is 1.
See these examples in
matlabroot/extern/examples/refbook
See these examples in
matlabroot/extern/examples/mx
See these examples in
matlabroot/extern/examples/mex
mxGetField,
mxGetFieldNameByNumber, mxGetFieldNumber, mxGetNumberOfFields, mxIsStruct,
mxSetField,
mxSetFieldByNumber