saving struct empty give me error

hi, it's possibile to save empty struct? How can i do it?

A=app.portFolio_struct;
 On=logical(str2double(A.List(:,2)));
 A.List=A.List(On,:);
 A.List=[];
 B=A.List; %memorizzo la struttura ma senza il setting !(e' caricato con un file a parte nel MPV_Serafini_PortfolioManager e poi messo in questa struttura )
 save(A.portFolio_setting.tslist,'-struct','B');
 
 Error using save
The argument to -STRUCT must be the name of a scalar structure variable.

Answer 1

[Stephen23]

"hi, it's possibile to save empty struct? How can i do it?"

Of course, just give the variable name exactly like you would any other variable:

S = struct('x',{},'y',{})

S = 

  0x0 empty struct array with fields:

    x
    y

save('mytest.mat','S') % no error

checking:

T = load('mytest.mat').S

T = 

  0x0 empty struct array with fields:

    x
    y

What will not work is the -struct option, which (as the error clearly states) only works for scalar structures. It also behaves differently, by saving each field as separate variables in the MAT file.

But there is absolutely no reason why you cannot save a structure of any size as its own variable.

Answer 2

[Animesh]

Hey @Luca Re,

The error message suggests that the variable you're trying to save with the "-struct" option is not a scalar structure. In this case, the variable "B" is causing the issue. To save an empty struct, ensure that you're saving a structure variable, even if it is empty. Here's how you can modify your code:

B = struct('List', A.List);
save(A.portFolio_setting.tslist, 'B');

In here, we create "B" as a structure with an empty field named "List".