mxSetFieldByNumber (External Interfaces/API Reference)

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

Fortran Syntax

subroutine mxSetFieldByNumber(pm, index, fieldnumber, value)
integer*4 pm, index, fieldnumber, value

Arguments

pm
Pointer to a structure mxArray. Call mxIsStruct to determine if pm points 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 fieldnumber of 1, the second field has a fieldnumber of 2, and so on. The last field has a fieldnumber of N, where N is the number of fields.

value
The value you are assigning. Use one of the mxCreate* functions to create the value mxArray.

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.

Description

Use mxSetFieldByNumber to assign a value to the specified element of the specified field. If there is already a value at the given position, the value pointer you specified overwrites the old value pointer. However, mxSetFieldByNumber does not free the dynamic memory that the old value pointer pointed to. Consequently, you are responsible for destroying this mxArray.

mxSetFieldByNumber is almost identical to mxSetField; however, the former takes a field number as its third argument, and the latter takes a field name as its third argument.

Calling

mxSetField(pm, index, 'fieldname', newvalue)

is equivalent to calling

fieldnum = mxGetFieldNumber(pm, 'fieldname')
mxSetFieldByNumber(pm, index, fieldnum, newvalue)

mxSetField mxSetImagData