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

loadmatfileMATLAB

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?
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