mxGetFieldNumber (External Interfaces/API Reference)

Get a field number, given a field name in a structure array

Fortran Syntax

integer*4 function mxGetFieldNumber(pm, fieldname)
integer*4 pm
character*(*) fieldname

Arguments

pm
Pointer to a structure mxArray.

fieldname
The name of a field in the structure mxArray.

Returns

The field number of the specified fieldname, on success. The first field has a field number of 1, the second field has a field number of 2, and so on. Returns 0 on failure. Common causes of failure include:

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

Specifying the fieldname of a nonexistent field.

Description

If you know the name of a field but do not know its field number, call mxGetFieldNumber. Conversely, if you know the field number but do not know its field name, call mxGetFieldNameByNumber.

For example, consider a MATLAB structure initialized to

patient.name = 'John Doe';
patient.billing = 127.00;
patient.test = [79 75 73; 180 178 177.5; 220 210 205];

The field name name has a field number of 1; the field name billing has a field number of 2; and the field name test has a field number of 3. If you call mxGetFieldNumber and specify a fieldname of anything other than 'name', 'billing', or 'test', then mxGetFieldNumber returns 0.

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 1-by-1 structure.

mxGetFieldNameByNumber mxGetImagData