Is it possible to use the LOAD function to load structure fields selectively in MATLAB?

I would like to load structure fields selectively in MATLAB using the LOAD function. For example, if I define the following structure:

a.x = 1;
a.y = 2;
save example a;

It is possible to selectively load the structure variable a:

load example a

I want to be able to selectively load only the x field of a.

Answer 1

[MathWorks Support Team]

Use the "-struct" option when saving MAT-files so that structure fields are saved as separate variables. You can then use the LOAD function to select particular variables from the MAT-file:

a.x = 1;
a.y = 2;
save('example','-struct','a');
clear all;
load('example','x');

The "-struct" option is not available prior to MATLAB 7.0 (R14).

Using the "struct" flag causes each field of the structure to be individual variables in the MAT-file. To load them back into a structure use:

>> a = load('example')

[K E]

Please supply an example for more recent releases that do not require this workaround. For more recent releases, it sounds like you wouldn't need the -struct flag when you save the file, but I can't get your original example to work in R2015b. [By the way this is hugely useful and I am surprised it is not better known, at least to me!]

[Guillaume]

I don't understand what "This enhancement has been incorporated in Release 2011b" refers to actually. It certainly does not refer to "I would like to load structure fields selectively" since that's not possible in any recent version of matlab, even if you use matfile.

[Guillaume]

Trust me for missing out the one important word! I meant to write "that's not possible in any recent version of matlab".

[K E]

A downside of the -struct flag is that the *.mat file contains a set of variables so I lose the original structure, unless I am missing something.

[Richard Crozier]

@K E, the advantage is that if you then use load on the same file like

S = load (filename)

It's put back into the structure again. In fact there's not a simple way to load variables from a file into a variable directly without them ending up in a structure.