mxGetFieldByNumber (External Interfaces/API Reference)

Get a field value, given a field number and an index in a structure array

Fortran Syntax

integer*4 function mxGetFieldByNumber(pm, index, fieldnumber)
integer*4 pm, index, fieldnumber

Arguments

pm
Pointer to a structure mxArray.

index
The desired element. The first element of an mxArray has an index of 1, the second element has an index of 2, and the last element has an index of N, where N is the total number of elements in the structure mxArray.

fieldnumber
The position of the field whose value you want to extract. 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.

Returns

A pointer to the mxArray in the specified field for the desired element, on success. Returns zero if passed an invalid argument or if there is no value assigned to the specified field. Common causes of failure include:

Specifying a pm that does not point to a structure mxArray. Call mxIsStruct to determine if pm points to is a structure mxArray.

Specifying an index < 1 or > the number of elements in the array.

Specifying a nonexistent field number. Call mxGetFieldNumber to determine the field number that corresponds to a given field name.

Description

Call mxGetFieldByNumber to get the value held in the specified fieldnumber at the indexed element.

Note Inputs to a MEX-file are constant read-only mxArrays and should not be modified. Using mxSetCell* or mxSetField* to modify the cells or fields of an argument passed from MATLAB causes unpredictable results.

Calling

```
mxGetField(pm, index, 'fieldname')
```

is equivalent to calling

fieldnum = mxGetFieldNumber(pm, 'fieldname')
mxGetFieldByNumber(pm, index, fieldnum)

where index is 1 if you have a one-by-one structure.

mxGetField mxGetFieldNameByNumber