Copying option structs by value instead of reference

14 views (last 30 days)
Here is an example using bodeoptions, but this is probably a much more basic problem:
% Create a struct with default values
opt1 = bodeoptions;
% Change a value
opt1.MagScale = 'log'
% Now generate another (?) struct with the same options
opt2 = opt1;
% Change the value in the original struct back to default
opt1.MagScale = 'linear'
% Surprise! The value is changed back in the 'copy,' too
Similarly, changing anything in opt2 changes opt1, too, so it appears opt2 is not another struct but a reference to the same structure as opt1.
Can anybody tell me what's happening here, and in particular: How would I create a copy of opt1 that I can change without changing opt1, too?

Accepted Answer

Guillaume on 18 Aug 2014
Most likely, bodeoptions returns a handle class rather than a structure.
whos opt1
would tell you.
Matlab does not have a built-in way to do deep copy of handle classes. Possibly, the class has a method to do this. You can check with
But in any case, what's stopping you from creating your second variable with:
opt2 = bodeoptions;
It'll start out the same as opt1 but will be a different object.
per isakson
per isakson on 18 Aug 2014
Edited: per isakson on 18 Aug 2014
Matlab is hiding something, or uses features, which are not yet documented. With R2013a
>> superclasses(opt1)
No superclasses for class plotopts.BodePlotOptions ...
Jonathan Epperl
Jonathan Epperl on 18 Aug 2014
With 2014a, I get
>> superclasses(opt1)
No class plotopts.BodePlotOptions

Sign in to comment.

More Answers (1)

Image Analyst
Image Analyst on 18 Aug 2014
Very interesting. It doesn't happen with simpler structures you make on your own:
s1.a = 10;
s1.b = 20;
% Make copy.
s2 = s1
% Change something in the original.
s1.a = 999
% Print to command window;
s2 % s2.a is not 999


Find more on Entering Commands in Help Center and File Exchange


Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!