Is their any way to load only selected fields from a saved structure array.

I have some very large structure arrays stored in .mat files. I want to avoid loading the entire array to save time and memory.

Answer 1

[Stephen23]

Method

Make sure you save the structure array using the '-struct' option:

 save(filename,'-struct','S')

And then, exactly as the load documentation says, you can load the variables by supplying their names as optional arguments. E.g. if the mat file contains variables X and Y:

 S = load(filename,'X','Y');

This will only load X and Y into the structure S, not matter what other variables are also present in the mat file.

Example

>> S.X = 1:3;
>> S.Y = 4:5;
>> S.Z = 6:9;
>> save('test.mat','-struct','S')
>> clear
>> S = load('test.mat','X','Y');
>> fieldnames(S)
ans =
    'X'
    'Y'
>> S.Y
ans =
   4   5

[Walter Roberson]

However, if they are structure arrays rather than scalar structures, then you cannot use save -struct

Answer 2

[Walter Roberson]

Sorry there is no Mathworks provided way to do that.

If you just happen to be using a v7.3 mat file then I wonder if there would be an approach by using hdf5 routines to access the mat file?