Using the C Math Library

Deleting Elements from a Structure Array

There are three kinds of deletion operations you can perform on a structure array.

You can delete:

• An entire structure from the array
• A field from all the structures in the array
• Elements from an array contained by a field

Deleting a Structure from the Array

To delete an entire structure from a structure array, use mlfIndexDelete(). For example, if you have a three-element array of image structures, you can delete the second image structure like this:

mlfIndexDelete(&images, "(?)", mlfScalar(2));

images(2) = [] performs the same operation in MATLAB. The result is a two-element array of image structures.

Deleting a Field from All the Structures in an Array

To delete a field from all the structures in the array, use mlfRmfield(). For example, you can remove the description field from an array of image structures with this code:

mlfAssign(&images, mlfRmfield(images,
                              mxCreateString("description")));

images = rmfield(images, 'description') performs the same operation in MATLAB.

Note that rmfield() does not allow you to remove a field of a nested structure from a structure array. For example, you cannot remove the day field of the nested date structure with this MATLAB code:

rmfield(images.date, 'day')

This is an error in MATLAB, and the corresponding call to mlfRmfield() is an error in the MATLAB C Math Library.

Deleting an Element from an Array Contained by a Field

To delete an element from an array contained by a field, use mlfIndexDelete(). For example, to remove the fifth column of the image in the third image structure, call mlfIndexDelete() like this:

mlfIndexDelete(&images, "(?).image(?,?)", 
               mlfScalar(3),
               mlfCreateColonIndex(),
               mlfScalar(5));

images(3).image(:,5) = [] performs the same operation in MATLAB.

Accessing the Contents of Structures Within Cells

Comparison of C and MATLAB Indexing Syntax