How to access a particular array from a structure of arrays saved in a .mat file without loading the entire mat file

Hi

I have a .mat file which contain a structure which in turn has many fields and large data arrays. Sample file shown below:

y_struct = struct('yval',[],'time',[]);
y_struct.yval = struct('tag',{'y1value','y2value','y3value'},'data',{[],[],[]});   %  Defining structure to store the y array 
                                                                                %  and its deviations 
y_struct.time = t;
y_struct.yval(1).data = input;                                                        
y_struct.yval(2).data = y_struct.yval(1).data + 0.5;

Load command will save the entire mat file in memory. In my application, I want to access data fields with a particular tag(y_struct.yval(1).data). Is there a way to directly access this array element without having to load the entire .mat file? I read that using a matfile object we can access mat file elements but is it possible to access array index?

Answer 1

[KSSV]

Read the link:

https://in.mathworks.com/help/matlab/import_export/load-parts-of-variables-from-mat-files.html

[Nadia A]

Can this method of accessing the mat file contents by objects also access the elements if it is a structure of arrays? I read that it cannot access indices like structure_name.fieldname(1).data

[KSSV]

What error it shows?

[Nadia A]

It says field cannot be accessed. The mat file contains 3 (1x4) structures. tag1,tag2,tag3(each of dimension 1x4). When I try to access data field of tag1, it shows error

'Cannot index into 'tag1' because MatFile objects only support '()' indexing'