MATLAB has a setfield and a rmfield, but not a "rename field". You need to write one for this problem.

Example

Suppose

 s(1).foo = 1;
 s(1).bar = 'one';
 s(2).foo = 2;
 s(2).bar = 'two';

and you want the field "bar" to be renamed "baz". Given the inputs s, oldField, and newField, you must return this output structure with all the data still in place.

 s(1).foo = 1;
 s(1).baz = 'one';
 s(2).foo = 2;
 s(2).baz = 'two';

[Problem from Matthew Simoneau]